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Sample records for vcsel polarization control

  1. Nonvolatile polarization control of a bistable VCSEL.

    PubMed

    Marconi, Mathias; Barland, Stéphane; Giudici, Massimo

    2012-12-10

    We report experimental evidence of nonvolatile all-optical memory operation using the two linear polarization states emitted from a GaAs oxide-confined VCSEL. The two polarization states coexist in a large range of pumping currents and substrate temperatures, and they can be controlled all-optically by exposing the device to polarization selective feedback, to crossed polarization reinjection orby injecting external light pulses. The active polarization state is recovered after powering off and on the VCSEL, while memory is lost if the substrate temperature is varied. PMID:23262865

  2. VCSEL polarization control for chip-scale atomic clocks.

    SciTech Connect

    Geib, Kent Martin; Peake, Gregory Merwin; Wendt, Joel Robert; Serkland, Darwin Keith; Keeler, Gordon Arthur

    2007-01-01

    Sandia National Laboratories and Mytek, LLC have collaborated to develop a monolithically-integrated vertical-cavity surface-emitting laser (VCSEL) assembly with controllable polarization states suitable for use in chip-scale atomic clocks. During the course of this work, a robust technique to provide polarization control was modeled and demonstrated. The technique uses deeply-etched surface gratings oriented at several different rotational angles to provide VCSEL polarization stability. A rigorous coupled-wave analysis (RCWA) model was used to optimize the design for high polarization selectivity and fabrication tolerance. The new approach to VCSEL polarization control may be useful in a number of defense and commercial applications, including chip-scale atomic clocks and other low-power atomic sensors.

  3. Volume production of polarization controlled single-mode VCSELs

    NASA Astrophysics Data System (ADS)

    Grabherr, Martin; King, Roger; Jäger, Roland; Wiedenmann, Dieter; Gerlach, Philipp; Duckeck, Denise; Wimmer, Christian

    2008-02-01

    Over the past 3 years laser based tracking systems for optical PC mice have outnumbered the traditional VCSEL market datacom by far. Whereas VCSEL for datacom in the 850 nm regime emit in multipe transverse modes, all laser based tracking systems demand for single-mode operation which require advanced manufacturing technology. Next generation tracking systems even require single-polarization characteristics in order to avoid unwanted movement of the pointer due to polarization flips. High volume manufacturing and optimized production methods are crucial for achieving the addressed technical and commercial targets of this consumer market. The resulting ideal laser source which emits single-mode and single-polarization at low cost is also a promising platform for further applications like tuneable diode laser absorption spectroscopy (TDLAS) or miniature atomic clocks when adapted to the according wavelengths.

  4. Controllable optoelectric composite logic gates based on the polarization switching in an optically injected VCSEL.

    PubMed

    Zhong, Dongzhou; Ji, Yongqiang; Luo, Wei

    2015-11-16

    Based on the polarization switching mechanism in an optically injected vertical cavity surface emitting laser (VCSEL), and the new electro-optic modulation theory, we propose a novel approach to implement optoelectric logic gates. Here, the two linearly polarized lights from the output of the laser are considered as two logic outputs. Under the electro-optic modulation, one of the logic outputs is the NOT operation with the other one. With the same logic input signal, we perform various digital signal processing (AND, OR, XNOR, NAND, NOR and XOR) in the optical domain, controlling the logic operation of the applied electric field between the two logic input signals. On this basis, the logic operation of half-adder is further implemented. PMID:26698465

  5. Polarization-resolved time-delay signatures of chaos induced by FBG-feedback in VCSEL

    E-print Network

    Chan, Sze-Chun

    Polarization-resolved time-delay signatures of chaos induced by FBG-feedback in VCSEL Zhu intensities from a vertical-cavity surface-emitting laser (VCSEL) subject to feedback from a fiber Bragg signatures. Finally, by comparing with a VCSEL subject to feedback from a mirror, the VCSEL subject

  6. Controllable spiking patterns in long-wavelength VCSELs for neuromorphic photonics systems

    E-print Network

    Hurtado, Antonio

    2015-01-01

    Multiple controllable spiking patterns are obtained in a 1310 nm Vertical Cavity Surface Emitting Laser (VCSEL) in response to induced perturbations and for two different cases of polarized optical injection, namely parallel and orthogonal. Achievement of reproducible spiking responses in VCSELs operating at the telecom wavelengths offers great promise for future uses of these devices in ultrafast neuromorphic photonic systems for non-traditional computing applications.

  7. Time-delay signature of chaos in 1550 nm VCSELs with variable-polarization FBG feedback.

    PubMed

    Li, Yan; Wu, Zheng-Mao; Zhong, Zhu-Qiang; Yang, Xian-Jie; Mao, Song; Xia, Guang-Qiong

    2014-08-11

    Based on the framework of spin-flip model (SFM), the output characteristics of a 1550 nm vertical-cavity surface-emitting laser (VCSEL) subject to variable-polarization fiber Bragg grating (FBG) feedback (VPFBGF) have been investigated. With the aid of the self-correlation function (SF) and the permutation entropy (PE) function, the time-delay signature (TDS) of chaos in the VPFBGF-VCSEL is evaluated, and then the influences of the operation parameters on the TDS of chaos are analyzed. The results show that the TDS of chaos can be suppressed efficiently through selecting suitable coupling coefficient and feedback rate of the FBG, and is weaker than that of chaos generated by traditional variable-polarization mirror feedback VCSELs (VPMF-VCSELs) or polarization-preserved FBG feedback VCSELs (PPFBGF-VCSELs). PMID:25321044

  8. Asymmetric dwell-time statistics of polarization chaos from free-running VCSEL.

    PubMed

    Virte, Martin; Mirisola, Elodie; Sciamanna, Marc; Panajotov, Krassimir

    2015-04-15

    We experimentally report on asymmetric dwell-time statistics of polarization chaos dynamics generated from free-running vertical-cavity surface-emitting lasers (VCSELs). Theoretically, we explain this behavior by introducing a misalignment between the phase and amplitude anisotropy within the spin-flip model for VCSELs. It induces an asymmetry in the VCSEL polarization behavior which is then responsible for significant changes in the statistics of the chaotic mode-hopping with an increase in the average residence time and an inversion of the dominant mode. PMID:25872094

  9. Optical injection induced polarization mode switching and correlation analysis on a VCSEL

    E-print Network

    Damodarakurup, Sajeev; Vudayagiri, Ashok

    2015-01-01

    Vertical cavity Surface Emitting Laser (VCSEL) diodes emit light in two polarization modes. The amount of optical feedback is found to influence the intensities of the emitted modes. We investigate the effect of the amount of total output polarization feedback and polarization selective feedback on the intensities of the two emitted polarization modes. A 40 micro seconds resolution time series correlation analysis is done for different feedback conditions and investigate the power spectral continuity and onset of chaos on two polarization modes

  10. Investigation of elliptically polarized injection locked states in VCSELs subject to orthogonal optical injection.

    PubMed

    Lin, Hong; Pérez, Pablo; Valle, Angel; Pesquera, Luis

    2014-03-10

    We demonstrate experimentally the existence of the elliptically polarized injection-locked (EPIL) state. This state is observed when a single-transverse mode VCSEL is subject to orthogonal optical injection. The spectral feature of the EPIL state is verified and the power of each polarization is measured. The regime of the EPIL state is identified in the parameter plane of frequency detuning and injection power for different bias currents. As current decreases the frequency detuning range for the EPIL to exist is narrower and shifts toward the negative frequency detuning. Periodic dynamics of the VCSEL is found in the neighborhood of the EPIL regime. PMID:24663827

  11. Novel closed-form solution for spin-polarization in quantum dot VCSEL

    NASA Astrophysics Data System (ADS)

    Qasaimeh, Omar

    2015-09-01

    A novel analytical model for spin-polarization in quantum dot VCSEL has been derived. The derived model includes the effect of spin relaxation of electron and hole in all discrete energy states. The model also takes into account the gain dispersion of the quantum dots, the birefringence, the linewidth enhancement factor and the doping concentration in the active layer. We find that spin relaxation of electrons has stronger effect on the polarization characteristics of quantum dot VCSEL than spin relaxation of holes (especially in p-type doped spin-injected quantum dot VCSEL). The derived model is accurate and exhibits negligible computational time compared with numerical models. In addition, the derived model is suitable for device design and optimization.

  12. All-optical 2-bit header recognition and packet switching using polarization bistable VCSELs.

    PubMed

    Hayashi, Daisuke; Nakao, Kazuya; Katayama, Takeo; Kawaguchi, Hitoshi

    2015-04-01

    We propose and evaluate an all-optical 2-bit header recognition and packet switching method using two 1.55-µm polarization bistable vertical-cavity surface-emitting lasers (VCSELs) and three optical switches. Polarization bistable VCSELs acted as flip-flop devices by using AND-gate operations of the header and set pulses, together with the reset pulses. Optical packets including 40-Gb/s non-return-to-zero pseudo-random bit-sequence payloads were successfully sent to one of four ports according to the state of two bits in the headers with a 4-bit 500-Mb/s return-to-zero format. The input pulse powers were 17.2 to 31.8 dB lower than the VCSEL output power. We also examined an extension of this method to multi-bit header recognition and packet switching. PMID:25968674

  13. Investigation of polarization switching of VCSEL subject to intensity modulated and optical feedback

    NASA Astrophysics Data System (ADS)

    Nazhan, Salam; Ghassemlooy, Z.; Busawon, K.; Gholami, A.

    2015-12-01

    This study presents the results of an experimental investigation of the polarization switching (PS) of vertical-cavity surface-emitting lasers (VCSELs) using the so-called polarization-rotated optical feedback mechanism. In particular, the experiments is performed by changing the laser driving current, optical feedback (OF) level, modulation signal parameters, such as frequency, modulation-depth in order to assess their influences on the PS of VCSEL. We show that a smaller polarization angle ?p is required to realize PS with increasing the level of OF. Moreover, for a fixed OF level and increased bias current a smaller ?p is required to ensure PS. However, for a fixed OF and variable modulation parameters, both the frequency and modulation-depth lead to the elimination of PS over the entire range of measurement.

  14. 1.55-?m VCSEL with polarization-independent HCG mirror on SOI.

    PubMed

    Tsunemi, Yoshihiro; Yokota, Nobuhide; Majima, Shota; Ikeda, Kazuhiro; Katayama, Takeo; Kawaguchi, Hitoshi

    2013-11-18

    We designed and fabricated a vertical-cavity surface-emitting laser (VCSEL) incorporating a polarization-independent high-index-contrast subwavelength grating (HCG) mirror on silicon-on-insulator (SOI) for a novel polarization-bistable device on a silicon substrate. The VCSEL consists of the HCG mirror, an active layer with InGaAsP quantum wells having optical gain around 1.55 ?m, and an Al0.9Ga0.1As/Al0.16Ga0.84As DBR. We used direct wafer bonding for the bonding between the active layer and the AlGaAs DBR, and benzocyclobutene (BCB) bonding for the bonding between the active layer and the polarization-independent HCG mirror. The reflectivity of the HCG embedded with BCB was measured, resulting in a 200-nm-high reflectivity band with reflectivity higher than 99% and a small polarization dependence of ± 1%. We achieved lasing of the fabricated HCG-VCSEL at 1527 nm under an optical short pulse excitation with an average power of 50 mW (~0.2 mJ/cm2) at 240 K. PMID:24514380

  15. Polarization-resolved time-delay signatures of chaos induced by FBG-feedback in VCSEL.

    PubMed

    Zhong, Zhu-Qiang; Li, Song-Sui; Chan, Sze-Chun; Xia, Guang-Qiong; Wu, Zheng-Mao

    2015-06-15

    Polarization-resolved chaotic emission intensities from a vertical-cavity surface-emitting laser (VCSEL) subject to feedback from a fiber Bragg grating (FBG) are numerically investigated. Time-delay (TD) signatures of the feedback are examined through various means including self-correlations of intensity time-series of individual polarizations, cross-correlation of intensities time-series between both polarizations, and permutation entropies calculated for the individual polarizations. The results show that the TD signatures can be clearly suppressed by selecting suitable operation parameters such as the feedback strength, FBG bandwidth, and Bragg frequency. Also, in the operational parameter space, numerical maps of TD signatures and effective bandwidths are obtained, which show regions of chaotic signals with both wide bandwidths and weak TD signatures. Finally, by comparing with a VCSEL subject to feedback from a mirror, the VCSEL subject to feedback from the FBG generally shows better concealment of the TD signatures with similar, or even wider, bandwidths. PMID:26193526

  16. Controlled switching of ultrafast circular polarization oscillations in spin-polarized vertical-cavity surface-emitting lasers

    SciTech Connect

    Höpfner, Henning Lindemann, Markus; Gerhardt, Nils C.; Hofmann, Martin R.

    2014-01-13

    We demonstrate a scheme for controlled switching of polarization oscillations in spin-polarized vertical-cavity surface-emitting lasers (spin-VCSEL). Under hybrid electrical and optical pumping conditions, our VCSEL devices show polarization oscillations with frequencies far above the VCSEL's electrical modulation bandwidth. Using multiple optical pulses, we are able to excite and amplify these polarization oscillations. When specific phase and amplitude conditions for the optical excitation pulses are met, destructive interference leads to switch-off of the polarization oscillation, enabling the generation of controlled short polarization bursts.

  17. Fast, electrically controlled polarization modulation of multimode vertical-cavity surface-emitting lasers by RF frequency modulation.

    PubMed

    Barve, Ajit V; Zheng, Yan; Johansson, Leif A; Mehta, Alok; Husain, Anis; Coldren, Larry A

    2013-12-16

    We report on a study of polarization properties of asymmetric, multimode vertical-cavity surface-emitting lasers (VCSEL) subjected to electrical RF modulation. When subjected to RF modulation, complex frequency-dependent polarization properties, especially near the polarization switching point are revealed. We propose a scheme of rapidly switching the two RF frequencies modulating the VCSEL, in order to achieve fast polarization modulation in these VCSEL. Polarization modulation up to 300 MHz by modulating the RF frequency and up to 1.5 GHz with RF power modulation has been demonstrated; the fastest reported electrically controlled polarization modulation for multimode VCSELs. PMID:24514683

  18. Effect of temperature on polarization switching in long-wavelength VCSELs

    NASA Astrophysics Data System (ADS)

    Quirce, Ana; Valle, Angel; Pesquera, Luis; Panajotov, Krassimir; Thienpont, Hugo

    2015-03-01

    We have measured the effect of the temperature on the polarization-resolved characteristics of a 1550-nm singletransverse mode vertical-cavity surface-emitting laser (VCSEL). Two double polarization switchings (PS) are observed. For low temperatures a PS from longer to shorter wavelengths (Type II PS) followed by the opposite PS (Type I) is observed. For higher temperatures Type I followed by Type II PS are measured. A simple expression relating the spin flip rate to the dichroism, differential gain, threshold current and PS current is derived. With this expression the dependence of the spin-flip rate on the temperature is obtained.

  19. Study on differences between high contrast grating reflectors for TM and TE polarizations and their impact on VCSEL designs

    E-print Network

    Chung, Il-Sug

    2015-01-01

    A theoretical study of differences in broadband high-index-contrast grating (HCG) reflectors for TM and TE polarizations is presented, covering various grating parameters and properties of HCGs. It is shown that the HCG reflectors for TM polarization (TM HCG reflectors) have much thicker grating thicknesses and smaller grating periods than the TE HCG reflectors. This difference is found to originate from the different boundary conditions met for the electric field of each polarization. Due to this difference, the TM HCG reflectors have much shorter evanescent extension of HCG modes into low-refractive-index media surrounding the HCG. This enables to achieve a very short effective cavity length for VCSELs, which is essential for ultrahigh speed VCSELs and MEMS-tunable VCSELs. The obtained understandings on polarization dependences will be able to serve as important design guidelines for various HCG-based devices.

  20. Study on differences between high contrast grating reflectors for TM and TE polarizations and their impact on VCSEL designs.

    PubMed

    Chung, Il-Sug

    2015-06-29

    A theoretical study of differences in broadband high-index-contrast grating (HCG) reflectors for TM and TE polarizations is presented, covering various grating parameters and properties of HCGs. It is shown that the HCG reflectors for TM polarization (TM HCG reflectors) have much thicker grating thicknesses and smaller grating periods than the TE HCG reflectors. This difference is found to originate from the different boundary conditions met for the electric field of each polarization. Due to this difference, the TM HCG reflectors have much shorter evanescent extension of HCG modes into low-refractive-index media surrounding the HCG. This enables to achieve a very short effective cavity length for VC-SELs, which is essential for ultrahigh speed VCSELs and MEMS-tunable VCSELs. The obtained understandings on polarization dependences will be able to serve as important design guidelines for various HCG-based devices. PMID:26191685

  1. Study on differences between high contrast grating reflectors for TM and TE polarizations and their impact on VCSEL designs

    NASA Astrophysics Data System (ADS)

    Chung, Il-Sug

    2015-06-01

    A theoretical study of differences in broadband high-index-contrast grating (HCG) reflectors for TM and TE polarizations is presented, covering various grating parameters and properties of HCGs. It is shown that the HCG reflectors for TM polarization (TM HCG reflectors) have much thicker grating thicknesses and smaller grating periods than the TE HCG reflectors. This difference is found to originate from the different boundary conditions met for the electric field of each polarization. Due to this difference, the TM HCG reflectors have much shorter evanescent extension of HCG modes into low-refractive-index media surrounding the HCG. This enables to achieve a very short effective cavity length for VCSELs, which is essential for ultrahigh speed VCSELs and MEMS-tunable VCSELs. The obtained understandings on polarization dependences will be able to serve as important design guidelines for various HCG-based devices.

  2. Transverse mode control in high-contrast grating VCSELs.

    PubMed

    G?bski, Marcin; Kuzior, Olga; Dems, Maciej; Wasiak, Micha?; Xie, Y Y; Xu, Z J; Wang, Qi Jie; Zhang, Dao Hua; Czyszanowski, Tomasz

    2014-08-25

    This paper presents an extensive numerical analysis of a high-contrast grating VCSEL emitting at 0.98 ?m. Using a three-dimensional, fully vectorial optical model, we investigate the influence of a non-uniform grating with a broad range of geometrical parameters on the modal behavior of the VCSEL. Properly designed and optimized, the high-contrast grating confines the fundamental mode selectively in all three dimensions and discriminates all higher order modes by expelling them from its central region. This mechanism makes single mode operation possible under a broad range of currents and could potentially enhance the single-mode output power of such devices. The high-contrast grating design proposed here is the only design for a VCSEL with three-dimensional, selective, optical confinement that requires relatively simple fabrication. PMID:25321296

  3. Power-induced polarization switching and bistability characteristics in 1550-nm VCSELs subjected to orthogonal optical injection

    NASA Astrophysics Data System (ADS)

    Chen, Jian-Jun; Xia, Guang-Qiong; Wu, Zheng-Mao

    2015-02-01

    The polarization switching (PS) and polarization bistability (PB) characteristics of a 1550-nm vertical-cavity surface-emitting laser (VCSEL) subjected to orthogonal optical injection are systematically investigated. The simulated results show that the PS and polarization-resolved nonlinear dynamical states of the VCSEL are critically dependent on the changing paths of the injected power. The polarization dynamics for different scanning directions of the injected power is presented to explain the polarization evolution during the formation of PS. In the case of forward scanning injected power, with the increase of frequency detuning level between the VCSEL and the injected light, the injected power required for PS gradually increases for negative frequency detuning but exhibits fluctuations for positive frequency detuning. In the case of reversely scanning injected power, the injected power required for PS displays fluctuant changes within the whole frequency detuning range. Specifically, PS may disappear under certain negative frequency detuning and large bias current. Furthermore, the hysteresis width as a function of the frequency detuning is calculated, and the regions for the appearance and disappearance of PB have been determined in the parameter space of the bias current and frequency detuning. Project supported by the National Natural Science Foundation of China (Grant Nos. 61178011, 61275116, and 61475127) and the Natural Science Foundation of Chongqing City, China (Grant No. 2012jjB40011).

  4. VCSEL-powered and polarization-maintaining fiber-optic grating vector rotation sensor.

    PubMed

    Guo, Tuan; Liu, Fu; Du, Fa; Zhang, Zhaochuan; Li, Chunjie; Guan, Bai-Ou; Albert, Jacques

    2013-08-12

    A compact fiber-optic vector rotation sensor in which a short section of polarization-maintaining (PM) fiber stub containing a straight fiber Bragg grating (FBG) is spliced to another single mode fiber without any lateral offset is proposed and experimentally demonstrated. Due to the intrinsic birefringence of the PM fiber, two well-defined resonances (i.e. orthogonally polarized FBG core modes) with wavelength separation of 0.5 nm have been achieved in reflection, and they exhibit a high sensitivity to fiber rotation. Both the orientation and the angle of rotation can be determined unambiguously via simple power detection of the relative amplitudes of the orthogonal core reflections. Meanwhile, instead of using a broadband source (BBS), the sensor is powered by a commercial vertical cavity surface emitting laser (VCSEL) with the laser wavelength matched to the PM-FBG core modes, which enables the sensor to work at much higher power levels (~15 dB better than BBS). This improves the signal-to-noise ratio considerably (~50 dB), and makes a demodulation filter unnecessary. Vector rotation measurement with a sensitivity of 0.09 dB/deg has been achieved via cost-effective single detector real time power measurement, and the unwanted power fluctuations and temperature perturbations can be effectively referenced out. PMID:23938824

  5. Long-haul dual-channel bidirectional chaos communication based on polarization-resolved chaos synchronization between twin 1550 nM VCSELs subject to variable-polarization optical injection

    NASA Astrophysics Data System (ADS)

    Wang, Ling; Wu, Zheng-Mao; Wu, Jia-Gui; Xia, Guang-Qiong

    2015-01-01

    Based on the polarization-resolved chaos synchronization between twin 1550 nm vertical-cavity surface-emitting lasers (VCSELs), a novel long-haul dual-channel bidirectional chaos communication system is proposed. In this system, a time delay signature (TDS)-suppressed chaotic signal, generated by a driving VCSEL (D-VCSEL) under double external cavity feedbacks (DECFs), simultaneously injects into twin VCSELs by variable-polarization optical injection (VPOI) to synchronize them and enhance the chaos output bandwidth of the two VCSELs. The simulated results show that, under proper injection parameters, high-quality polarization-resolved chaos synchronization between the twin VCSELs can be achieved; meanwhile the bandwidths of chaotic signals output from the twin VCSELs have been enhanced in comparison with that of the driven chaotic signal. Based on the high-quality polarization-resolved chaos synchronization, after adopting polarization-division-multiplexing (PDM) and chaos masking (CM) techniques, four 10 Gb/s messages hidden respectively in four chaotic carriers can be decrypted effectively after propagating 15 km in single-mode fiber (SMF) links. After adopting dispersion-shifted fibers (DSFs) as fiber links, the dual-channel bidirectional chaos communication distance can be extended to 140 km.

  6. Control of emitted light polarization in a 1310?nm dilute nitride spin-vertical cavity surface emitting laser subject to circularly polarized optical injection

    SciTech Connect

    Alharthi, S. S. Hurtado, A.; Al Seyab, R. K.; Henning, I. D.; Adams, M. J.; Korpijarvi, V.-M.; Guina, M.

    2014-11-03

    We experimentally demonstrate the control of the light polarization emitted by a 1310?nm dilute nitride spin-Vertical Cavity Surface Emitting Laser (VCSEL) at room temperature. This is achieved by means of a combination of polarized optical pumping and polarized optical injection. Without external injection, the polarization of the optical pump controls that of the spin-VCSEL. However, the addition of the externally injected signal polarized with either left- (LCP) or right-circular polarization (RCP) is able to control the polarization of the spin-VCSEL switching it at will to left- or right-circular polarization. A numerical model has been developed showing a very high degree of agreement with the experimental findings.

  7. Ultrafast polarization dynamics with controlled polarization oscillations in vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Lindemann, Markus; Höpfner, Henning; Gerhardt, Nils C.; Hofmann, Martin R.; Pusch, Tobias; Michalzik, Rainer

    2015-03-01

    Spintronic lasers offer promising perspectives for new concepts superior to options of purely charge-based devices. Especially spin-polarized vertical-cavity surface-emitting lasers (spin-VCSELs) exhibit ultrafast spin and polarization dynamics. Using pulsed spin-injection, oscillations in the circular polarization degree can be generated, which have the potential to exceed frequencies of 100 GHz. The oscillations evolve due to coupling of the carrier-spin-photon system for linear modes via birefringence in the VCSEL's cavity. They are independent of the conventional relaxation oscillations and thus their usage can be the cornerstone for ultrafast directly modulated spin-VCSELs in the near future. After giving a short overview of the state of scientific and technical knowledge we will outline a method to control the polarization oscillations by multiple spin-injection pulses. It is possible to switch these oscillations on and off, depending on phase and amplitude conditions of two consecutive excitation pulses. Even half-cycles can be generated, which is the basis for short polarization pulses, only limited by the polarization oscillation resonance frequency. We investigate influences of the birefringence, which directly determines the oscillation frequency, by means of calculations with the spin-flip-model and experimental verification using 850 nm VCSELs. Furthermore we discuss experimental possibilities of increasing the birefringence and therefore the oscillation frequency, such that ultrashort pulses come into reach.

  8. Hybrid VCSEL: liquid crystal systems

    NASA Astrophysics Data System (ADS)

    Panajotov, K.; Xie, Y.; Beeckman, J.; Neyts, K.; Dems, M.; Belmonte, C.; Thienpont, H.

    2015-03-01

    We study theoretically and experimentally spectral and polarization characteristics of hybrid systems of VCSELs integrated within liquid crystal (LC) cells. Three cases are considered: Nematic or cholesteric LC on top of VCSEL, coupled-cavity system with the second cavity next to the VCSEL's one filled in with nematic LC and a system with a nematic LC inside the VCSEL cavity. For the case of nematic liquid crystal - VCSEL coupled cavity system we demonstrate selection between two orthogonal directions of linear polarization of the fundamental mode by changing the LC length or by electro-optical tuning of the LC director. For the case of cholesteric liquid crystal-VCSEL system we demonstrate lasing on circularly polarized (CP) modes due to the LC band gap for CP light. The transition from nematic to isotropic phase of the LC when increasing temperature leads to a drastic change of the polarization of the generated light from left-handed circular to linear polarization. Finally, we investigate the possibility of efficient wavelength tuning by utilizing electrooptical effect in nematic LC layer integrated next to the active region in a VCSEL cavity.

  9. Nonpolar Gallium Nitride-based VCSELs

    NASA Astrophysics Data System (ADS)

    Holder, Casey Oliver

    GaN vertical-cavity surface-emitting lasers (VCSELs) are of increasing interest as sources of high-quality coherent light in the visible spectrum, particularly in blue wavelengths. These devices so far suffer from many problems, including low output power, low yield, and high costs. Nonpolar GaN offers many advantages for VCSELs. Anisotropic electric fields in the plane of the emitting quantum wells results in higher gain and crystallographically-oriented polarization of emitted light. This should result in the unique property of polarization locking, whereby the polarization direction of each device is identical, and determined by the crystal structure of the material in the device. Prior demonstrations of GaN VCSELs have relied on epitaxially-grown n-DBR mirrors, or mechanical polishing to remove the substrate to allow for deposition of dielectric DBR mirrors. Epitaxially-grown DBRs give epitaxial control of cavity length, but are very difficult and costly to grow. Mechanical polishing and deposition of dielectric DBRs simplifies fabrication, but gives no control of cavity length. This thesis reports on a novel fabrication method using photoelectrochemical (PEC) etching that gives epitaxial control of cavity length, while still allowing for the use of dielectric DBR mirrors. Using this novel fabrication method, the first nonpolar GaN-based VCSELs are demonstrated. These devices exhibit polarization locking, where each device is highly polarized parallel to the crystallographic a-direction of the wurtzite crystal structure. Electrically-injected lasing under pulsed operation at room temperature is reported, with an output power of approximately 20 uW at a wavelength of 411.9 nm.

  10. Invited Paper Subwavelength Transmission Gratings and Their Applications in VCSELs

    E-print Network

    Invited Paper Subwavelength Transmission Gratings and Their Applications in VCSELs Stephen Y. Choua (VCSELs) are presented. Particularly, large birefringence (over two orders of magnitude larger than of VCSELs (i.e., fixing, enhancing and switching of the polarization), making he maximum polarization

  11. Bistability of time-periodic polarization dynamics in a free-running VCSEL.

    PubMed

    Virte, M; Sciamanna, M; Mercier, E; Panajotov, K

    2014-03-24

    We report experimentally a bistability between two limit cycles (i.e. time-periodic dynamics) in a free-running vertical-cavity surface-emitting laser. The two limit cycles originate from a bifurcation on two elliptically polarized states which exhibit a small frequency difference and whose main axes are symmetrical with respect to the linear polarization eigenaxes at threshold. We demonstrate theoretically that this peculiar behavior can be explained in the framework of the spin-flip model model by taking into account a small misalignment between the phase and amplitude anisotropies. PMID:24664025

  12. VCSEL Meeting January13, 2012

    E-print Network

    Gan, K. K.

    VCSEL Meeting 1 January13, 2012 K.K. Gan Comparison of Optical Spectrum Width of VCSELs on Opto-boards vs Low-Humidity Test at OSU K.K. Gan The Ohio State University #12;K.K. Gan VCSEL Meeting 2 Spectrum Width of LAr VCSELs All but one failed VCSELs have narrow width All VCSELs

  13. Chaos breaking mechanism in solitary VCSELs

    E-print Network

    Virte, Martin

    2015-01-01

    In this letter, a new mechanism limiting the range of parameters for which polarization chaos dynamics in solitary VCSELs can appear is theoretically highlighted and investigated. We show that, even though another linearly polarized steady-state is stable, polarization chaos can appear because an unstable periodic orbit isolates the two dynamics. In certain conditions, however, this barrier becomes ineffective leading to the complete disappearance of the chaotic dynamics. Here, we clarify this mechanism and its effect on the VCSEL dynamics. In addition, we link the emergence of a different barrier orbit to a qualitative change in the polarization chaos dynamics.

  14. Chaos breaking mechanism in solitary VCSELs

    E-print Network

    Martin Virte

    2015-10-22

    In this letter, a new mechanism limiting the range of parameters for which polarization chaos dynamics in solitary VCSELs can appear is theoretically highlighted and investigated. We show that, even though another linearly polarized steady-state is stable, polarization chaos can appear because an unstable periodic orbit isolates the two dynamics. In certain conditions, however, this barrier becomes ineffective leading to the complete disappearance of the chaotic dynamics. Here, we clarify this mechanism and its effect on the VCSEL dynamics. In addition, we link the emergence of a different barrier orbit to a qualitative change in the polarization chaos dynamics.

  15. High-power VCSEL systems and applications

    NASA Astrophysics Data System (ADS)

    Moench, Holger; Conrads, Ralf; Deppe, Carsten; Derra, Guenther; Gronenborn, Stephan; Gu, Xi; Heusler, Gero; Kolb, Johanna; Miller, Michael; Pekarski, Pavel; Pollmann-Retsch, Jens; Pruijmboom, Armand; Weichmann, Ulrich

    2015-03-01

    Easy system design, compactness and a uniform power distribution define the basic advantages of high power VCSEL systems. Full addressability in space and time add new dimensions for optimization and enable "digital photonic production". Many thermal processes benefit from the improved control i.e. heat is applied exactly where and when it is needed. The compact VCSEL systems can be integrated into most manufacturing equipment, replacing batch processes using large furnaces and reducing energy consumption. This paper will present how recent technological development of high power VCSEL systems will extend efficiency and flexibility of thermal processes and replace not only laser systems, lamps and furnaces but enable new ways of production. High power VCSEL systems are made from many VCSEL chips, each comprising thousands of low power VCSELs. Systems scalable in power from watts to multiple ten kilowatts and with various form factors utilize a common modular building block concept. Designs for reliable high power VCSEL arrays and systems can be developed and tested on each building block level and benefit from the low power density and excellent reliability of the VCSELs. Furthermore advanced assembly concepts aim to reduce the number of individual processes and components and make the whole system even more simple and reliable.

  16. VCSEL-based photonic crystal heterostructures

    NASA Astrophysics Data System (ADS)

    Kapon, E.; Lundeberg, L. D. A.; Guerrero, G.; Lousberg, G. P.; Boiko, D. L.

    2006-02-01

    Phase-coupled arrays of vertical cavity surface emitting lasers (VCSELs) constitute a particular class of two-dimensional photonic crystal (PhC) structures in which the refractive index varies periodically in the plan normal to the beam propagation direction. The relatively simple implementation of these structures via lithography techniques permits the exploration of novel PhC configurations and the realization of novel spatial-mode-controlled VCSEL array structures. We review here the properties of VCSEL-based PhC structures realized using Bragg mirror patterning. Design and control of the photonic envelope functions in these devices using a variety of PhC homostructures and heterostructures are demonstrated and discussed. Potential applications of these structures in high power VCSELs, dynamic beam switching and optical image processing are mentioned.

  17. VCSEL Reliability in ATLAS and development of robust arrays

    E-print Network

    Weidberg, A R; The ATLAS collaboration

    2011-01-01

    Vertical Cavity Surface Emitting Lasers (VCSELs) are used for the readout and control of all ATLAS detectors at the LHC. Reliable VCSELs have been developed by using extensive Failure Analysis (FA) to eliminate or reduce the rates of random failures. Some of these FA techniques are described with illustrations from failed VCSEL channels from ATLAS operation. However VCSELs are very sensitive to several environmental factors. The reliability of the VCSELs in the different systems has been very varied. In addition to FA, controlled experiments have also been very useful in determining the cause of failures. The programmes to mitigate these failures for the two systems most affected are reviwed. A summary of VCSEL reliability and the outlook for ATLAS operation is given.

  18. VCSEL Applications and Simulation

    NASA Technical Reports Server (NTRS)

    Cheung, Samson; Goorjian, Peter; Ning, Cun-Zheng; Li, Jian-Zhong

    2000-01-01

    This viewgraph presentation gives an overview of Vertical Cavity Surface Emitting Laser (VCSEL) simulation and its applications. Details are given on the optical interconnection in information technology of VCSEL, the formulation of the simulation, its numeric algorithm, and the computational results.

  19. Controlled switching and frequency tuning of polarization oscillations in vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Lindemann, Markus; Höpfner, Henning; Gerhardt, Nils C.; Hofmann, Martin R.; Pusch, Tobias; Michalzik, Rainer

    2015-09-01

    Spintronic lasers offer promising perspectives for novel concepts and characteristics superior to conventional purely charge-based devices. This applies in particular to spin-polarized vertical-cavity surface-emitting lasers (spin-VCSELs), which exhibit ultrafast spin and polarization dynamics. Using pulsed spin-injection, oscillations in the circular polarization degree can be generated, which have the potential to be much faster than conventional relaxation oscillations and may exceed frequencies of 100 GHz. The oscillations originate from the coupled carrier-spin-photon system in birefringent VCSEL cavities. The polarization oscillations are independent from conventional relaxation oscillations and thus can be the cornerstone for ultrafast directly modulated spin-VCSELs in the near future. It is possible to switch the oscillations on and off, depending on phase and amplitude conditions of two consecutive excitation pulses. Even half-cycles can be generated, which is the basis for short polarization pulses, only limited by the polarization oscillation resonance frequency. Experimental results of oscillation switching are given using an 850 nm oxide-confined single-mode VCSEL. In order to increase the polarization oscillation frequency, the birefringence has to be tuned to higher values. We demonstrate a method to manipulate the birefringence by adding mechanical strain to the substrate in vicinity of the VCSEL. With this method the polarization oscillation frequency can be tuned over a wide range. The results are compared to the theory with simulations using the spin-flip-model.

  20. Interferometric polarization control

    NASA Technical Reports Server (NTRS)

    Wollack, Edward J. (Inventor); Moseley, Samuel H. (Inventor); Novak, Giles A. (Inventor); Chuss, David T. (Inventor)

    2009-01-01

    A signal conditioning module provides a polarimeter capability in a photometric system. The module may include multiple variable delay polarization modulators. Each modulator may include an input port, and a first arm formed to include a first reflector and first rooftop mirror arranged in opposed relationship. The first reflector may direct an input radiation signal to the first rooftop mirror. Each modulator also may include an output port and a second arm formed to include a second reflector and second rooftop mirror arranged in opposed relationship. The second reflector can guide a signal from the second rooftop mirror towards the output port to provide an output radiation signal. A beamsplitting grid may be placed between the first reflector and the first rooftop mirror, and also between the second reflector and the second rooftop mirror. A translation apparatus can provide adjustment relative to optical path length vis-a-vis the first arm, the second arm and the grid.

  1. Interferometric Polarization Control

    NASA Technical Reports Server (NTRS)

    Chuss, David T. (Inventor); Wollack, Edward J. (Inventor); Moseley, Samuel H. (Inventor); Novak, Giles A. (Inventor)

    2008-01-01

    A signal conditioning module provides a polarimeter capability in a photometric system. The module may include multiple variable delay polarization modulators. Each modulator may include an input port, and a first arm formed to include a first reflector and first rooftop mirror arranged in opposed relationship. The first reflector may direct an input radiation signal to the first rooftop mirror. Each modulator also may include an output port and a second arm formed to include a second reflector and second rooftop mirror arranged in opposed relationship. The second reflector can guide a signal from the second rooftop mirror towards the output port to provide an output radiation signal. A beamsplitting grid may be placed between the first reflector and the first rooftop mirror, and also between the second reflector and the second rooftop mirror. A translation apparatus can provide adjustment relative to optical path length vis-a-vis the first arm, the second arm and the grid.

  2. Computational optoelectromechanics and its application to MEMS VCSELs

    NASA Astrophysics Data System (ADS)

    Lyshevski, Sergey E.

    2003-04-01

    Vertical-cavity surface-emitting lasers (VCSELs) have been research extensively as key components for next-generation of wireless communication, computing, processing, switching and optical devices. Conventional VCSELs integrate two oppositely doped distributed Bragg reflectors (DBR) with a cavity layer between them. In the center of the cavity layer there is an active region with multiple quantum wells. Current is injected into the active region using oxide or proton-implanted apertures. Recent research and developments have been progressed to the tunable, long-wavelength, and multiple-wavelength MEMS-based electrically- and optically-pumped VCSELs. These MEMS VCSELs integrate a bottom n-DBR (for example, GaAs-AlGaAs), a cavity layer with the active region (for example, InGaAS), and a top mirror. The top mirror integrates p-DBR (oxidation and sacrificial layers, AlAs, AlGaAs) -- air gap -- top n-DBR suspended above the laser cavity and controlled (displaced or bent) by the nano- or microscale actuators. The current is fed through the p-DBR. Hence, optoelectronics and microelectromechics are examined for MEMS VCSELs. In contrast, the optically-pumped VCSLEs with membrane MEMS integrate n-DBR, cavity layer with the active region, p-DBR, sacrificial layer (for example, AlGaAs) and top mirror (quarter-wave GaAs layer). Usually, the wavelength of tunable VCSELs can be varied within 10 - 30 nm increments. To optimize MEMS VCSELs, far-reaching research and developments must be carried out. Recently, novel MEMS VCSELs topologies and configurations have been devised. These MEMS VCSELs must be modeled, analyzed, and optimized. The computer-aided-design will lead to essential improvement of lasers optimizing their performance. High-fidelity modeling, heterogeneous simulation, data-intensive analysis and synergetic design of MEMS VCSELs are part of a newly emerging field of computational optoelectromechanics. In fact, high-fidelity modeling is an important part in synthesis and design of affordable high-performance MEMS VCSELs with the desired performance and reliability. The basic equations to model VCSELs are found using the quantum mechanics, quantum electromagnetic field theory, Maxwell's and Navier-Stokes equations. To derive the equations of motion for nano- or microactuators, the functional density concept is used to find the force, and Newtonian mechanics allows one to derive the differential equations to integrate mechanical dynamics. This paper focuses on the development of the theory of computational optoelectromechanics and its application to computer-aided design of MEMS VCSELs. The modeling, simulation, analysis and design results are reported and illustrated.

  3. Circular polarization switching and bistability in an optically injected 1300 nm spin-vertical cavity surface emitting laser

    NASA Astrophysics Data System (ADS)

    Alharthi, S. S.; Hurtado, A.; Korpijarvi, V.-M.; Guina, M.; Henning, I. D.; Adams, M. J.

    2015-01-01

    We report the experimental observation of circular polarization switching (PS) and polarization bistability (PB) in a 1300 nm dilute nitride spin-vertical cavity surface emitting laser (VCSEL). We demonstrate that the circularly polarized optical signal at 1300 nm can gradually or abruptly switch the polarization ellipticity of the spin-VCSEL from right-to-left circular polarization and vice versa. Moreover, different forms of PS and PB between right- and left-circular polarizations are observed by controlling the injection strength and the initial wavelength detuning. These results obtained at the telecom wavelength of 1300 nm open the door for novel uses of spin-VCSELs in polarization sensitive applications in future optical systems.

  4. VCSEL Meeting 1 April 15, 2011

    E-print Network

    Gan, K. K.

    VCSEL Meeting 1 April 15, 2011 K.K. Gan Some Analyses of VCSEL Problem K.K. Gan The Ohio State University Reliability statistics on AOC and ULM VCSEL arrays Analysis of 9 channels on opto-boards with no light #12;K.K. Gan VCSEL Meeting 2 ULM Reliability Data produced ~50 wafers of 10 G and ~20 wafers

  5. Dynamic Self-Locking of an OEO Containing a VCSEL

    NASA Technical Reports Server (NTRS)

    Strekalov, Dmitry; Matsko, Andrey; Yu, Nan; Savchenkov, Anatoliy; Maleki, Lute

    2009-01-01

    A method of dynamic self-locking has been demonstrated to be effective as a means of stabilizing the wavelength of light emitted by a vertical-cavity surface-emitting laser (VCSEL) that is an active element in the frequency-control loop of an optoelectronic oscillator (OEO) designed to implement an atomic clock based on an electromagnetically- induced-transparency (EIT) resonance. This scheme can be considered an alternative to the one described in Optical Injection Locking of a VCSEL in an OEO (NPO-43454), NASA Tech Briefs, Vol. 33, No. 7 (July 2009), page 33. Both schemes are expected to enable the development of small, low-power, high-stability atomic clocks that would be suitable for use in applications involving precise navigation and/or communication. To recapitulate from the cited prior article: In one essential aspect of operation of an OEO of the type described above, a microwave modulation signal is coupled into the VCSEL. Heretofore, it has been well known that the wavelength of light emitted by a VCSEL depends on its temperature and drive current, necessitating thorough stabilization of these operational parameters. Recently, it was discovered that the wavelength also depends on the microwave power coupled into the VCSEL. This concludes the background information. From the perspective that led to the conception of the optical injection-locking scheme described in the cited prior article, the variation of the VCSEL wavelength with the microwave power circulating in the frequency-control loop is regarded as a disadvantage and optical injection locking is a solution of the problem of stabilizing the wavelength in the presence of uncontrolled fluctuations in the microwave power. The present scheme for dynamic self-locking emerges from a different perspective, in which the dependence of VCSEL wavelength on microwave power is regarded as an advantageous phenomenon that can be exploited as a means of controlling the wavelength. The figure schematically depicts an atomic-clock OEO of the type in question, wherein (1) the light from the VCSEL is used to excite an EIT resonance in selected atoms in a gas cell (e.g., 87Rb atoms in a low-pressure mixture of Ar and Ne) and (2) the power supplied to the VCSEL is modulated by a microwave signal that includes components at beat frequencies among the VCSEL wavelength and modulation sidebands. As the VCSEL wavelength changes, it moves closer to or farther from a nearby absorption spectral line, and the optical power transmitted through the cell (and thus the loop gain) changes accordingly. A change in the loop gain causes a change in the microwave power and, thus, in the VCSEL wavelength. It is possible to choose a set of design and operational parameters (most importantly, the electronic part of the loop gain) such that the OEO stabilizes itself in the sense that an increase in circulating microwave power causes the VCSEL wavelength to change in a direction that results in an increase in optical absorption and thus a decrease in circulating microwave power. Typically, such an appropriate choice of operational parameters involves setting the nominal VCSEL wavelength to a point on the shorter-wavelength wing of an absorption spectral line.

  6. Author's personal copy Thermal analysis of oxide-confined VCSEL arrays$

    E-print Network

    Friedman, Eby G.

    surface emitting laser (VCSEL) arrays based on the finite element method (FEM) is presented in this paper Savidis b,n , Eby G. Friedman b a The College of Electronic Information and Control Engineering, Beijing Keywords: Vertical cavity surface emitting lasers (VCSEL) Three-dimensional (3-D) modeling Thermal analysis

  7. LW VCSELs for SFP+ applications

    NASA Astrophysics Data System (ADS)

    Graham, Luke A.; Jewell, Jack L.; Maranowski, Kevin D.; Crom, Max V.; Feld, Stewart A.; Smith, Joseph M.; Beltran, James G.; Fanning, Thomas R.; Schnoes, Melinda; Gray, Matthew H.; Droege, David; Koleva, Vera; Dudek, Mike; Fiers, John; Patterson, Russ

    2008-02-01

    This article outlines development work at JDSU on InGaNAs based vertical cavity surface emitting lasers (VCSELs) operating at 1270nm and their use in 10Gbps SFP+ modules. DC and AC performance of die and transmit optical subassemblies (TOSAs) will be described. Due to their low power consumption, LW VCSELs are ideal for use in SFP+; module performance will be described as well.

  8. High power VCSELs for miniature optical sensors

    NASA Astrophysics Data System (ADS)

    Geske, Jon; Wang, Chad; MacDougal, Michael; Stahl, Ron; Follman, David; Garrett, Henry; Meyrath, Todd; Snyder, Don; Golden, Eric; Wagener, Jeff; Foley, Jason

    2010-02-01

    Recent advances in Vertical-cavity Surface-emitting Laser (VCSEL) efficiency and packaging have opened up alternative applications for VCSELs that leverage their inherent advantages over light emitting diodes and edge-emitting lasers (EELs), such as low-divergence symmetric emission, wavelength stability, and inherent 2-D array fabrication. Improvements in reproducible highly efficient VCSELs have allowed VCSELs to be considered for high power and high brightness applications. In this talk, Aerius will discuss recent advances with Aerius' VCSELs and application of these VCSELs to miniature optical sensors such as rangefinders and illuminators.

  9. Polarization dynamics in spin-polarized vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Gerhardt, Nils C.; Höpfner, Henning; Lindemann, Markus; Hofmann, Martin R.

    2014-08-01

    Spin-polarized lasers and especially spin-polarized vertical-cavity surface-emitting lasers (spin-VCSELs) are at- tractive novel spintronic devices providing functionalities and characteristics superior to their conventional purely charge-based counterparts. This applies in particular to ultrafast dynamics, modulation capability and chirp control of directly modulated lasers. Here we demonstrate that ultrafast oscillations of the circular polarization degree can be generated in VCSELs by pulsed spin injection which have the potential to reach frequencies beyond 100 GHz. These oscillations are due to the coupling of the carrier-spin-photon system via the optical birefringence for the linearly polarized laser modes in the micro-cavity and are principally decoupled from conventional relaxation oscillations of the carrier-photon system. Utilizing these polarization oscillations is a very promising path to ultrafast directly modulated spin-VCSELs in the near future as long as an effective concept can be developed to modulate or switch these polarization oscillations. After briefly reviewing the state of research in the emerging field of spin-VCSELs, we present a novel concept for controlled switching of polarization oscillations by use of multiple optical spin injection pulses. Depending on the amplitude and phase conditions of the excitation pulses, constructive or destructive interference of polarization oscillations leads to an excitation, stabilization or switch-off of these oscillations. Furthermore even short single polarization bursts can be generated with pulse widths only limited by the resonance frequency of the polarization oscillation. Consequently, this concept is an important building block for using spin controlled polarization oscillations for future communication applications.

  10. Nuclear reactivity control using laser induced polarization

    DOEpatents

    Bowman, Charles D. (Los Alamos, NM)

    1990-01-01

    A control element for reactivity control of a fission source provides an atomic density of .sup.3 He in a control volume which is effective to control criticality as the .sup.3 He is spin-polarized. Spin-polarization of the .sup.3 He affects the cross section of the control volume for fission neturons and hence, the reactivity. An irradiation source is directed within the .sup.3 He for spin-polarizing the .sup.3 He. An alkali-metal vapor may be included with the .sup.3 He where a laser spin-polarizes the alkali-metal atoms which in turn, spin-couple with .sup.3 He to spin-polarize the .sup.3 He atoms.

  11. Nuclear reactivity control using laser induced polarization

    DOEpatents

    Bowman, Charles D. (Los Alamos, NM)

    1991-01-01

    A control element for reactivity control of a fission source provides an atomic density of .sup.3 He in a control volume which is effective to control criticality as the .sup.3 He is spin-polarized. Spin-polarization of the .sup.3 He affects the cross section of the control volume for fission neutrons and hence, the reactivity. An irradiation source is directed within the .sup.3 He for spin-polarizing the .sup.3 He. An alkali-metal vapor may be included with the .sup.3 He where a laser spin-polarizes the alkali-metal atoms which in turn, spin-couple with .sup.3 He to spin-polarize the .sup.3 He atoms.

  12. VCSEL array-based light exposure system for laser printing

    NASA Astrophysics Data System (ADS)

    Mukoyama, Naotaka; Otoma, Hiromi; Sakurai, Jun; Ueki, Nobuaki; Nakayama, Hideo

    2008-02-01

    Improving the image quality and speed is an endless demand for printer applications. To meet the market requirements, we have launched the world first laser printer (DocuColor 1256 GA) introducing 780-nm single-mode 8×4 VCSEL arrays in the light exposure system in 2003. The DocuColor 1256 GA features 2400 dots per inch (dpi) resolution which is the highest in the industry and a speed of 50 pages per minute (ppm). A VCSEL array design has an advantage that it can increase the pixel density and also increase the printing speed by simultaneously scanning the 32-beam to the photoconductor in the exposure process. Adopting VCSELs as a light source also contributes to the reduction of the machine's power consumption. The VCSELs are industrially manufactured based on the original in-situ monitored oxidation process to control the oxide aperture size. As a result, uniform characteristics with a less than 5% variation in both output power and divergence angle are obtained. Special care is also taken in the assembly process to avoid additional degradation in performance and quality. This technology is currently extended to high-end tandem color machines (2400 dpi, 80 ppm) to grasp on-demand publishing market. This paper will cover the key technologies of the VCSEL based light exposure system as well as its manufacturing process to assure its quality.

  13. Ultrafast spin-polarized vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Gerhardt, Nils C.; Höpfner, Henning; Lindemann, Markus; Li, Mingyuan; Jähme, Hendrik; Ackemann, Thorsten; Hofmann, Martin R.

    2013-09-01

    Spin-polarized lasers are highly attractive spintronic devices providing characteristics superior to their conventional purely charge-based counterparts. Spin-polarized vertical-cavity surface emitting lasers (spin-VCSELs) promise to offer lower thresholds, enhanced emission intensity, spin amplification, full polarization control, chirp control and ultrafast dynamics. In particular, the ability to control and modulate the polarization state of the laser emission with extraordinarily high frequencies is very attractive for many applications like broadband optical communication and ultrafast optical switches. After briefly reviewing the state of research in this emerging field of spintronics, we present a novel concept for ultrafast spin-VCSELs which has the potential to overcome the conventional speed limitation for directly modulated lasers and to reach modulation frequencies significantly above 100 GHz. The concept is based on the coupled spin-photon dynamics in birefringent micro-cavity lasers. By injecting spin-polarized carriers in the VCSEL, oscillations of the coupled spin-photon system can by induced which lead to oscillations of the polarization state of the laser emission. These oscillations are decoupled from conventional relaxation oscillations of the carrier-photon system and can be much faster than those. Utilizing these polarization oscillations is thus a very promising approach to develop ultrafast spin-VCSELs for high speed optical data communication in the near future.

  14. Optical Injection Locking of a VCSEL in an OEO

    NASA Technical Reports Server (NTRS)

    Strekalov, Dmitry; Matsko, Andrey; Savchenkov, Anatoliy; Yu, Nan; Maleki, Lute

    2009-01-01

    Optical injection locking has been demonstrated to be effective as a means of stabilizing the wavelength of light emitted by a vertical-cavity surface- emitting laser (VCSEL) that is an active element in the frequency-control loop of an opto-electronic oscillator (OEO) designed to implement an atomic clock based on an electromagnetically- induced-transparency resonance. This particular optical-injection- locking scheme is expected to enable the development of small, low-power, high-stability atomic clocks that would be suitable for use in applications involving precise navigation and/or communication. In one essential aspect of operation of an OEO of the type described above, a microwave modulation signal is coupled into the VCSEL. Heretofore, it has been well known that the wavelength of light emitted by a VCSEL depends on its temperature and drive current, necessitating thorough stabilization of these operational parameters. Recently, it was discovered that the wavelength also depends on the microwave power coupled into the VCSEL. Inasmuch as the microwave power circulating in the frequency-control loop is a dynamic frequency-control variable (and, hence, cannot be stabilized), there arises a need for another means of stabilizing the wavelength. The present optical-injection-locking scheme satisfies the need for a means to stabilize the wavelength against microwave- power fluctuations. It is also expected to afford stabilization against temperature and current fluctuations. In an experiment performed to demonstrate this scheme, wavelength locking was observed when about 200 W of the output power of a commercial tunable diode laser was injected into a commercial VCSEL, designed to operate in the wavelength range of 795+/-3 nm, that was generating about 200 microW of optical power. (The use of relatively high injection power levels is a usual practice in injection locking of VCSELs.)

  15. K.K. Gan 1 Measurement of VCSEL Lifetime

    E-print Network

    Gan, K. K.

    VCSEL Priority of various tests is to measure lifetime of installed VCSELs understanding failure ~50 VCSEL arrays from original production 400 channels will be monitored represents during first month VCSEL Study Group Meeting #12;VCSEL Study Group Meeting 5 Test Setup Design

  16. Fast beam steering with full polarization control using a galvanometric optical scanner and polarization controller

    E-print Network

    Jofre, M; Steinlechner, F; Oliverio, N; Torres, J P; Pruneri, V; Mitchell, M W; 10.1364/OE.20.012247

    2012-01-01

    Optical beam steering is a key element in many industrial and scientific applications like in material processing, information technologies, medical imaging and laser display. Even though galvanometer-based scanners offer flexibility, speed and accuracy at a relatively low cost, they still lack the necessary control over the polarization required for certain applications. We report on the development of a polarization steerable system assembled with a fiber polarization controller and a galvanometric scanner, both controlled by a digital signal processor board. The system implements control of the polarization decoupled from the pointing direction through a feed-forward control scheme. This enables to direct optical beams to a desired direction without affecting its initial polarization state. When considering the full working field of view, we are able to compensate polarization angle errors larger than 0.2 rad, in a temporal window of less than $\\sim 20$ ms. Given the unification of components to fully cont...

  17. SASE FEL Polarization Control Using Crossed Undulator

    SciTech Connect

    Ding, Yuantao; Huang, Zhirong; /SLAC

    2008-09-30

    There is a growing interest in producing intense, coherent x-ray radiation with an adjustable and arbitrary polarization state. In this paper, we study the crossed undulator scheme for rapid polarization control in a self-amplified spontaneous emission (SASE) free electron laser (FEL). Because a SASE source is a temporally chaotic light, we perform a statistical analysis on the state of polarization using FEL theory and simulations. We show that by adding a small phase shifter and a short (about 1.3 times the FEL power gain length), 90{sup o} rotated planar undulator after the main SASE planar undulator, one can obtain circularly polarized light--with over 80% polarization--near the FEL saturation.

  18. Ultrafast Narrow Band Modulation of VCSELs

    NASA Technical Reports Server (NTRS)

    Ning, Cun-Zheng; Biegel, Bryan A. (Technical Monitor)

    2002-01-01

    Multimode beating was greatly enhanced by taking output from part (e.g., half) of the output facet. Simpler sources of microwaves and millimeter waves of various frequencies were generated by varying the VCSEL diameter in a single multimode VCSEL our coupling of a few VCSELs. Breathing frequency in multi-mode operations affects modulation response and bandwidth. Optimizing RO frequency and mode beating frequency could potentially expand bandwidths suitable for wide band digital communications.

  19. Double high refractive-index contrast grating VCSEL

    NASA Astrophysics Data System (ADS)

    Gebski, Marcin; Dems, Maciej; Wasiak, Micha?; Sarza?a, Robert P.; Lott, J. A.; Czyszanowski, Tomasz

    2015-03-01

    Distributed Bragg reflectors (DBRs) are typically used as the highly reflecting mirrors of vertical-cavity surface-emitting lasers (VCSELs). In order to provide optical field confinement, oxide apertures are often incorporated in the process of the selective wet oxidation of high aluminum-content DBR layers. This technology has some potential drawbacks such as difficulty in controlling the uniformity of the oxide aperture diameters across a large-diameter (? 6 inch) production wafers, high DBR series resistance especially for small diameters below about 5 ?m despite elaborate grading and doping schemes, free carrier absorption at longer emission wavelengths in the p-doped DBRs, reduced reliability for oxide apertures placed close to the quantum wells, and low thermal conductivity for transporting heat away from the active region. A prospective alternative mirror is a high refractive index contrast grating (HCG) monolithically integrated with the VCSEL cavity. Two HCG mirrors potentially offer a very compact and simplified VCSEL design although the problems of resistance, heat dissipation, and reliability are not completely solved. We present an analysis of a double HCG 980 nm GaAs-based ultra-thin VCSEL. We analyze the optical confinement of such a structure with a total optical thickness is ~1.0? including the optical cavity and the two opposing and parallel HCG mirrors.

  20. Organic photovoltaic cells with controlled polarization sensitivity

    SciTech Connect

    Awartani, Omar; O'Connor, Brendan T.; Kudenov, Michael W.

    2014-03-03

    In this study, we demonstrate linearly polarized organic photovoltaic cells with a well-controlled level of polarization sensitivity. The polarized devices were created through the application of a large uniaxial strain to the bulk heterojunction poly(3-hexylthiophene):Phenyl-C61-butyric acid methyl ester (P3HT:PCBM) film and printing the plastically deformed active layer onto a PEDOT:PSS and indium tin oxide coated glass substrate. The P3HT:PCBM layer is processed such that it is able to accommodate high strains (over 100%) without fracture. After printing the strained films, thermal annealing is used to optimize solar cell performance while maintaining polarization sensitivity. A dichroic ratio and short circuit current ratio of ?6.1 and ?1.6 were achieved, respectively.

  1. High-speed VCSELs and VCSEL arrays for single- and multi-core fiber interconnects

    NASA Astrophysics Data System (ADS)

    Larsson, Anders; Westbergh, Petter; Gustavsson, Johan S.; Haglund, Erik; Haglund, Emanuel P.

    2015-03-01

    Our recent work on high speed 850 nm VCSELs and VCSEL arrays is reviewed. With a modulation bandwidth approaching 30 GHz, our VCSELs have enabled transmitters and links operating at data rates in excess of 70 Gbps (at IBM) and transmission over onboard polymer waveguides at 40 Gbps (at University of Cambridge). VCSELs with an integrated mode filter for single mode emission have enabled transmission at 25 Gbps over >1 km of multimode fiber and a speed-distance product of 40 Gbps·km. Dense VCSEL arrays for multicore fiber interconnects have demonstrated 240 Gbps aggregate capacity with excellent uniformity and low crosstalk between the 40 Gbps channels.

  2. Fast beam steering with full polarization control using a galvanometric optical scanner and polarization controller.

    PubMed

    Jofre, M; Anzolin, G; Steinlechner, F; Oliverio, N; Torres, J P; Pruneri, V; Mitchell, M W

    2012-05-21

    Optical beam steering is a key element in many industrial and scientific applications like in material processing, information technologies, medical imaging and laser display. Even though galvanometer-based scanners offer flexibility, speed and accuracy at a relatively low cost, they still lack the necessary control over the polarization required for certain applications. We report on the development of a polarization steerable system assembled with a fiber polarization controller and a galvanometric scanner, both controlled by a digital signal processor board. The system implements control of the polarization decoupled from the pointing direction through a feed-forward control scheme. This enables to direct optical beams to a desired direction without affecting its initial polarization state. When considering the full working field of view, we are able to compensate polarization angle errors larger than 0.2 rad, in a temporal window of less than ? 20 ms. Given the unification of components to fully control any polarization state while steering an optical beam, the proposed system is potentially integrable and robust. PMID:22714214

  3. Ultrafast Directional Beam Switching in Coupled VCSELs

    NASA Technical Reports Server (NTRS)

    Ning, Cun-Zheng; Goorjian, Peter

    2001-01-01

    We propose a new approach to performing ultrafast directional beam switching using two coupled Vertical-Cavity Surface-Emitting Lasers (VCSELs). The proposed strategy is demonstrated for two VCSELs of 5.6 microns in diameter placed about 1 micron apart from the edges, showing a switching speed of 42 GHz with a maximum far-field angle span of about 10 degrees.

  4. Fabrication issues of oxide-confined VCSELs

    SciTech Connect

    Geib, K.M.; Choquette, K.D.; Hou, H.Q.; Hammons, B.E.

    1997-04-01

    To insert high-performance oxide-confined vertical-cavity surface- emitting lasers (VCSELs) into the manufacturing arena, we have examined the critical parameters that must be controlled to establish a repeatable and uniform wet thermal oxidation process for AlGaAs. These parameters include the AlAs mole fraction, sample temperature, carrier gas flow, and bubbler water temperature. Knowledge of these parameters has enable the compilation of oxidation rate data for AlGaAs which exhibits an Arrhenius rate dependence. The compositionally dependent activation energies for Al{sub x}Ga{sub 1-x}As layers of x=1.00, 0.98, and 0.92 are found to be 1.24, 1.75, and 1.88 eV, respectively. 7 figs, 1 tab, 14 refs.

  5. Analysis of waveguiding properties of VCSEL structures

    SciTech Connect

    Erteza, I.A.

    1996-09-01

    In this paper, the authors explore the feasibility of using the distributed Bragg reflector, grown on the substrate for a VCSEL (Vertical Cavity Surface Emitting Laser), to provide waveguiding within the substrate. This waveguiding could serve as an interconnection among VCSELs in an array. Before determining the feasibility of waveguide interconnected VCSELs, two analysis methods are presented and evaluated for their applicability to this problem. The implementations in Mathematica of both these methods are included. Results of the analysis show that waveguiding in VCSEL structures is feasible. Some of the many possible uses of waveguide interconnected VCSELs are also briefly discussed. The tools and analysis presented in this report can be used to evaluate such system concepts and to do detailed design calculations.

  6. Interface control of bulk ferroelectric polarization

    PubMed Central

    Yu, P.; Luo, W.; Yi, D.; Zhang, J. X.; Rossell, M. D.; Yang, C.-H.; You, L.; Singh-Bhalla, G.; Yang, S. Y.; He, Q.; Ramasse, Q. M.; Erni, R.; Martin, L. W.; Chu, Y. H.; Pantelides, S. T.; Pennycook, S. J.; Ramesh, R.

    2012-01-01

    The control of material interfaces at the atomic level has led to novel interfacial properties and functionalities. In particular, the study of polar discontinuities at interfaces between complex oxides lies at the frontier of modern condensed matter research. Here we employ a combination of experimental measurements and theoretical calculations to demonstrate the control of a bulk property, namely ferroelectric polarization, of a heteroepitaxial bilayer by precise atomic-scale interface engineering. More specifically, the control is achieved by exploiting the interfacial valence mismatch to influence the electrostatic potential step across the interface, which manifests itself as the biased-voltage in ferroelectric hysteresis loops and determines the ferroelectric state. A broad study of diverse systems comprising different ferroelectrics and conducting perovskite underlayers extends the generality of this phenomenon. PMID:22647612

  7. Communication using VCSEL laser array

    NASA Technical Reports Server (NTRS)

    Goorjian, Peter M. (Inventor)

    2008-01-01

    Ultrafast directional beam switching, using coupled vertical cavity surface emitting lasers (VCSELs) is combined with a light modulator to provide information transfer at bit rates of tens of GHz. This approach is demonstrated to achieve beam switching frequencies of 32-50 GHz in some embodiments and directional beam switching with angular differences of about eight degrees. This switching scheme is likely to be useful for ultrafast optical networks at frequencies much higher than achievable with other approaches. A Mach-Zehnder interferometer, a Fabry-Perot etalon, or a semiconductor-based electro-absorption transmission channel, among others, can be used as a light modulator.

  8. Advanced Concepts for High-Power VCSELS and 2-Dimensional VCSEL Arrays

    SciTech Connect

    Allerman, A.A.; Choquette, Kent D.; Chow, W.W.; Geib, K.M.; Hadley, R.; Hou, H.Q.; Mar, A.

    1999-04-01

    We have developed high power vertical cavity surface emitting lasers (VCSELS) for multimode or single mode operation. We have characterized new cavity designs for individual lasers and 2-dimensional VCSEL arrays to maximize output power. Using broad area high power VCSELS under pulsed excitation, we have demonstrated the triggering of a photoconductive semiconductor switch (PCSS) with a VCSEL. We also have developed designs for high output power in a single mode. The first approach is to engineer the oxide aperture profile to influence the optical confinement and thus modal properties. A second approach focuses on "leaky-mode" concepts using lateral modification of the cavity resonance to provide the lateral refractive index difference. To this end, we have developed a regrowth process to fabricate single-mode VCSELS. The overall objective of this work was to develop high-power single-mode or multimode sources appropriate for many applications leveraging the many inherent advantages of VCSELS.

  9. Long wavelength VCSEL-by-VCSEL optically injection locked optoelectronic oscillator

    NASA Astrophysics Data System (ADS)

    Coronel, Juan; Varón, Margarita; Rissons, Angélique

    2015-03-01

    In this article we propose a long wavelength VCSEL by VCSEL Optoelectronic Oscillator to generate high frequency carriers. Stability and quality are key factors to use Vertical-Cavity Surface-Emitting Lasers (VCSELs) in VCSEL Based Optoelectronic Oscillators (VBO). To enhance the performance of a 2.49 GHz VBO presented in [1]. The use of the optical injection locking technique applied to the VBO laser pump contributes to the VCSEL Relative Intensity Noise (RIN) reduction, and the increase of the modulation bandwidth that leads to a carrier phase noise reduction. The Injection Locked VCSEL Based Oscillator (ILVBO) performance will be presented and discussed taking into account the injection locking conditions of the laser source.

  10. VCSEL`s bonded directly to foundry fabricated GaAs smart pixel arrays

    SciTech Connect

    Pu, R.; Hayes, E.M.; Jurrat, R.; Wilmsen, C.W.; Choquette, K.D.; Hou, H.Q.; Geib, K.M.

    1997-12-01

    This letter reports the flip-chip bonding of an 8 x 8 array of free standing VCSEL`s to a foundry fabricated GaAs metal-semiconductor field-effect transistor (MESFET) smart pixel array. The VCSEL`s have oxide defined apertures and are co-planar bonded directly to smart pixels which perform the selection function of a data filter. The V{sub th} and series resistance of the VCSEL`s were on average approximately 2.1 V and 250 {Omega}, respectively, which indicates that good electrical contact was obtainable with this process. The I{sub th} ranged between 2--4 mA, with a corresponding output power of between 400 {micro}W and >1.0 mW depending on aperture size.

  11. Ultrafast Beam Switching Using Coupled VCSELs

    NASA Technical Reports Server (NTRS)

    Ning, Cun-Zheng; Goorjian, Peter

    2001-01-01

    We propose a new approach to performing ultrafast beam switching using two coupled Vertical-Cavity Surface-Emitting Lasers (VCSELs). The strategy is demonstrated by numerical simulation, showing a beam switching of 10 deg at 42 GHz.

  12. Controlling Polar Molecules in Optical Lattices

    E-print Network

    S. Kotochigova; E. Tiesinga

    2006-02-01

    We investigate theoretically the interaction of polar molecules with optical lattices and microwave fields. We demonstrate the existence of frequency windows in the optical domain where the complex internal structure of the molecule does not influence the trapping potential of the lattice. In such frequency windows the Franck-Condon factors are so small that near-resonant interaction of vibrational levels of the molecule with the lattice fields have a negligible contribution to the polarizability and light-induced decoherences are kept to a minimum. In addition, we show that microwave fields can induce a tunable dipole-dipole interaction between ground-state rotationally symmetric (J=0) molecules. A combination of a carefully chosen lattice frequency and microwave-controlled interaction between molecules will enable trapping of polar molecules in a lattice and possibly realize molecular quantum logic gates. Our results are based on ab initio relativistic electronic structure calculations of the polar KRb and RbCs molecules combined with calculations of their rovibrational motion.

  13. Polarization control in GaN nanowire lasers.

    PubMed

    Xu, Huiwen; Hurtado, Antonio; Wright, Jeremy B; Li, Changyi; Liu, Sheng; Figiel, Jeffrey J; Luk, Ting-Shan; Brueck, Steven R J; Brener, Igal; Balakrishnan, Ganesh; Li, Qiming; Wang, George T

    2014-08-11

    We demonstrate polarization control in optically-pumped single GaN nanowire lasers fabricated by a top-down method. By placing the GaN nanowires onto gold substrates, the naturally occurring randomly orientated elliptical polarization of nanowire lasers is converted to a linear polarization that is oriented parallel to the substrate surface. Confirmed by simulation results, this polarization control is attributed to a polarization-dependent loss induced by the gold substrate, which breaks the mode degeneracy of the nanowire and forms two orthogonally polarized modes with largely different cavity losses. PMID:25321005

  14. Development of polarization-mode controllable CARS microscope

    NASA Astrophysics Data System (ADS)

    Hashimoto, Mamoru; Takagi, Tatsuro; Minamikawa, Takeo; Niioka, Hirohiko; Araki, Tsutomu

    2011-03-01

    We developed a polarization-mode controllable coherent anti-Stokes Raman scattering microscope. The polarizationmode of excitations beams such as linear, radial, or azimuth polarization were switched with compact polarization mode converters made of eight-segmented liquid-crystal spatial-light-modulators. The polarization-mode of the excitation beams is electrically controllable without any mechanical operation. We demonstrated the detection of the molecular orientation of liquid crystals with the developed microscope.

  15. Properties of small-aperture selectively oxidized VCSELs

    SciTech Connect

    Choquette, K.D.; Chow, W.W.; Hadley, G.R.; Hou, H.Q.; Geib, K.M.

    1996-12-31

    We report an analysis of the size dependence of VCSEL threshold which agrees with experimental results. The increasing threshold current density of small area VCSELs arises from both increasing threshold gain and increasing leakage current.

  16. Broadband laser polarization control with aligned carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Yang, He; Fu, Bo; Li, Diao; Tian, Ying; Chen, Ya; Mattila, Marco; Yong, Zhenzhong; Li, Ru; Hassanien, Abdou; Yang, Changxi; Tittonen, Ilkka; Ren, Zhaoyu; Bai, Jintao; Li, Qingwen; Kauppinen, Esko I.; Lipsanen, Harri; Sun, Zhipei

    2015-06-01

    We introduce a simple approach to fabricate an aligned carbon nanotube (ACNT) device for broadband polarization control in fiber laser systems. The ACNT device was fabricated by pulling from as-fabricated vertically-aligned carbon nanotube arrays. Their anisotropic properties are confirmed with various microscopy techniques. The device was then integrated into fiber laser systems (at two technologically important wavelengths of 1 and 1.5 ?m) for polarization control. We obtained a linearly-polarized light output with the maximum extinction ratio of ~12 dB. The output polarization direction could be fully controlled by the ACNT alignment direction in both lasers. To the best of our knowledge, this is the first time that the ACNT device is applied to polarization control in laser systems. Our results exhibit that the ACNT device is a simple, low-cost, and broadband polarizer to control laser polarization dynamics, for various photonic applications (such as material processing, polarization diversity detection in communications etc.), where linear polarization control is necessary.We introduce a simple approach to fabricate an aligned carbon nanotube (ACNT) device for broadband polarization control in fiber laser systems. The ACNT device was fabricated by pulling from as-fabricated vertically-aligned carbon nanotube arrays. Their anisotropic properties are confirmed with various microscopy techniques. The device was then integrated into fiber laser systems (at two technologically important wavelengths of 1 and 1.5 ?m) for polarization control. We obtained a linearly-polarized light output with the maximum extinction ratio of ~12 dB. The output polarization direction could be fully controlled by the ACNT alignment direction in both lasers. To the best of our knowledge, this is the first time that the ACNT device is applied to polarization control in laser systems. Our results exhibit that the ACNT device is a simple, low-cost, and broadband polarizer to control laser polarization dynamics, for various photonic applications (such as material processing, polarization diversity detection in communications etc.), where linear polarization control is necessary. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01904d

  17. Modelling of optical synchronization of chaotic external cavity VCSELs

    E-print Network

    Colet, Pere

    Modelling of optical synchronization of chaotic external cavity VCSELs P.S.Spencer \\Lambda of a master­slave configuration for effecting the synchronization of chaotic VCSELs is studied using numerical simulations. The dynamical evolution of optically coupled VCSELs is examined using a travelling wave model

  18. Advances and new functions of VCSEL photonics

    NASA Astrophysics Data System (ADS)

    Koyama, Fumio

    2014-11-01

    A vertical cavity surface emitting laser (VCSEL) was born in Japan. The 37 years' research and developments opened up various applications including datacom, sensors, optical interconnects, spectroscopy, optical storages, printers, laser displays, laser radar, atomic clock and high power sources. A lot of unique features have been already proven, such as low power consumption, a wafer level testing and so on. The market of VCSELs has been growing up rapidly and they are now key devices in local area networks based on multi-mode optical fibers. Optical interconnections in data centers and supercomputers are attracting much interest. In this paper, the advances on VCSEL photonics will be reviewed. We present the high-speed modulation of VCSELs based on a coupled cavity structure. For further increase in transmission capacity per fiber, the wavelength engineering of VCSEL arrays is discussed, which includes the wavelength stabilization and wavelength tuning based on a micro-machined cantilever structure. We also address a lateral integration platform and new functions, including high-resolution beam scanner, vortex beam creation and large-port free space wavelength selective switch with a Bragg reflector waveguide.

  19. Process control system using polarizing interferometer

    DOEpatents

    Schultz, T.J.; Kotidis, P.A.; Woodroffe, J.A.; Rostler, P.S.

    1994-02-15

    A system for nondestructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading. 38 figures.

  20. Furnace control apparatus using polarizing interferometer

    DOEpatents

    Schultz, Thomas J. (Maumee, OH); Kotidis, Petros A. (Waban, MA); Woodroffe, Jaime A. (North Reading, MA); Rostler, Peter S. (Newton, MA)

    1995-01-01

    A system for non-destructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading.

  1. Furnace control apparatus using polarizing interferometer

    DOEpatents

    Schultz, T.J.; Kotidis, P.A.; Woodroffe, J.A.; Rostler, P.S.

    1995-03-28

    A system for nondestructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading. 38 figures.

  2. Process control system using polarizing interferometer

    DOEpatents

    Schultz, Thomas J. (Maumee, OH); Kotidis, Petros A. (Waban, MA); Woodroffe, Jaime A. (North Reading, MA); Rostler, Peter S. (Newton, MA)

    1994-01-01

    A system for non-destructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading.

  3. VCSEL applications in sensors and microsystems

    SciTech Connect

    Warren, M.E.; Carson, R.F.; Sweatt, W.C.; Wendt, J.R.; Nevers, J.A.; Crawford, M.H.; Hou, H.Q.

    1998-01-01

    Vertical-cavity surface-emitting lasers (VCSELs) are uniquely suited to miniaturized free-space optical systems in which surface-mounting and hybrid assembly techniques can be used to combine different technologies together. Two examples are described of such microsystems that are being developed for sensing applications. The first example is a optical position sensing system for rotating parts. Progress on fabricating similar systems by flip-chip bonding techniques is then discussed. The second example is a chemical sensing/analysis system which uses a miniature fluorescence detection module that is based on surface-mounted VCSELs and diffractive optical elements. The detection module is integrated with a capillary electrochromatography separation system and uses substrate-mode light propagation to focus the VCSEL beam on the capillary channel.

  4. VCSEL based, wearable, continuously monitoring pulse oximeter.

    PubMed

    Kollmann, Daniel; Hogan, William K; Steidl, Charles; Hibbs-Brenner, Mary K; Hedin, Daniel S; Lichter, Patrick A

    2013-01-01

    We present the development of a novel pulse oximeter based on low power, low cost, Vertical Cavity Surface Emitting Laser (VCSEL) technology. This new design will help address a need to perform regular measurements of pulse oximetry for patients with chronic obstructive pulmonary disease. VCSELs with wavelengths suitable for pulse oximetry were developed and packaged in a PLCC package for a low cost solution that is easy to integrate into a pulse oximeter design. The VCSELs were integrated into a prototype pulse oximeter that is unobtrusive and suitable for long term wearable use. The prototype achieved good performance compared the Nonin Onyx II pulse oximeter at less than one fifth the weight in a design that can be worn behind the ear like a hearing aid. PMID:24110647

  5. All-optical polarization control and noise cleaning based on a nonlinear lossless polarizer

    NASA Astrophysics Data System (ADS)

    Barozzi, Matteo; Vannucci, Armando; Picchi, Giorgio

    2015-01-01

    We propose an all-optical fiber-based device able to accomplish both polarization control and OSNR enhancement of an amplitude modulated optical signal, affected by unpolarized additive white Gaussian noise, at the same time. The proposed noise cleaning device is made of a nonlinear lossless polarizer (NLP), that performs polarization control, followed by an ideal polarizing filter that removes the orthogonally polarized half of additive noise. The NLP transforms every input signal polarization into a unique, well defined output polarization (without any loss of signal energy) and its task is to impose a signal polarization aligned with the transparent eigenstate of the polarizing filter. In order to effectively control the polarization of the modulated signal, we show that two different NLP configurations (with counter- or co-propagating pump laser) are needed, as a function of the signal polarization coherence time. The NLP is designed so that polarization attraction is effective only on the "noiseless" (i.e., information-bearing) component of the signal and not on noise, that remains unpolarized at the NLP output. Hence, the proposed device is able to discriminate signal power (that is preserved) from in-band noise power (that is partly suppressed). Since signal repolarization is detrimental if applied to polarization-multiplexed formats, the noise cleaner application is limited here to "legacy" links, with 10 Gb/s OOK modulation, still representing the most common format in deployed networks. By employing the appropriate NLP configurations, we obtain an OSNR gain close to 3dB. Furthermore, we show how the achievable OSNR gain can be estimated theoretically.

  6. Robust design of Si/Si3N4 high contrast grating mirror for mid-infrared VCSEL application

    E-print Network

    Chevallier, Christyves; Genty, Frédéric; Jacquet, Joel

    2012-01-01

    A Si/Si3N4 high contrast grating mirror has been designed for a VCSEL integration in mid-infrared ({\\lambda} = 2.65 $\\mu$m). The use of an optimization algorithm which maximizes a VCSEL mirror quality factor allowed the adjustment of the grating parameters while keeping large and shallow grating pattern. The robustness with respect to fabrication error has been enhanced thanks to a precise study of the grating dimension tolerances. The final mirror exhibits large high reflectivity bandwidth with a polarization selectivity and several percent of tolerance on the grating dimensions.

  7. Observation of electro-activated localized structures in broad area VCSELs

    E-print Network

    Parravicini, J; Columbo, L; Prati, F; Rizza, C; Tissoni, G; Agranat, A J; DelRe, E

    2014-01-01

    We demonstrate experimentally the electro-activation of a localized optical structure in a coherently driven broad-area vertical-cavity surface-emitting laser (VCSEL) operated below threshold. Control is achieved by electro-optically steering a writing beam through a pre-programmable switch based on a photorefractive funnel waveguide.

  8. Observation of electro-activated localized structures in broad area VCSELs.

    PubMed

    Parravicini, J; Brambilla, M; Columbo, L; Prati, F; Rizza, C; Tissoni, G; Agranat, A J; DelRe, E

    2014-12-01

    We demonstrate experimentally the electro-activation of a localized optical structure in a coherently driven broad-area vertical-cavity surface-emitting laser (VCSEL) operated below threshold. Control is achieved by electro-optically steering a writing beam through a pre-programmable switch based on a photorefractive funnel waveguide. PMID:25606953

  9. K.K. Gan 1 Plan for Truelight VCSEL Lifetime Study

    E-print Network

    Gan, K. K.

    K.K. Gan 1 Plan for Truelight VCSEL Lifetime Study July 26, 2010 K.K. Gan The Ohio State University #12;K.K. Gan 2 Outline Introduction Optical spectrum of aged VCSEL channels Plan on VCSEL lifetime study with opto-boards Plan on VCSEL lifetime study with opto-packs Candidate VCSELs for new

  10. Optical power of VCSELs stabilized to 35 ppm/°C without a TEC

    NASA Astrophysics Data System (ADS)

    Downing, John

    2015-03-01

    This paper reports a method and system comprising a light source, an electronic method, and a calibration procedure for stabilizing the optical power of vertical-cavity surface-emitting lasers (VCSELs) and laser diodes (LDs) without the use thermoelectric coolers (TECs). The system eliminates the needs for custom interference coatings, polarization adjustments, and the exact alignment required by the optical method reported in 2013 [1]. It can precisely compensate for the effects of temperature and wavelength drift on photodiode responsivity as well as changes in VCSEL beam quality and polarization angle over a 50°C temperature range. Data obtained from light sources built with single-mode polarization-locked VCSELs demonstrate that 30 ppm/°C stability can be readily obtained. The system has advantages over TECstabilized laser modules that include: 1) 90% lower relative RMS optical power and temperature sensitivity, 2) a five-fold enhancement of wall-plug efficiency, 3) less component testing and sorting, 4) lower manufacturing costs, and 5) automated calibration in batches at time of manufacture is practical. The system is ideally suited for battery-powered environmental and in-home medical monitoring applications.

  11. VCSEL-based parallel optical transmission module

    NASA Astrophysics Data System (ADS)

    Shen, Rongxuan; Chen, Hongda; Zuo, Chao; Pei, Weihua; Zhou, Yi; Tang, Jun

    2005-02-01

    This paper describes the design process and performance of the optimized parallel optical transmission module. Based on 1×12 VCSEL (Vertical Cavity Surface Emitting Laser) array, we designed and fabricated the high speed parallel optical modules. Our parallel optical module contains a 1×12 VCSEL array, a 12 channel CMOS laser driver circuit, a high speed PCB (Printed Circuit Board), a MT fiber connector and a packaging housing. The L-I-V characteristics of the 850nm VCSEL was measured at the operating current 8mA, 3dB frequency bandwidth more than 3GHz and the optical output 1mW. The transmission rate of all 12 channels is 30Gbit/s, with a single channel 2.5Gbit/s. By adopting the integration of the 1×12 VCSEL array and the driver array, we make a high speed PCB (Printed Circuit Board) to provide the optoelectronic chip with the operating voltage and high speed signals current. The LVDS (Low-Voltage Differential Signals) was set as the input signal to achieve better high frequency performance. The active coupling was adopted with a MT connector (8° slant fiber array). We used the Small Form Factor Pluggable (SFP) packaging. With the edge connector, the module could be inserted into the system dispense with bonding process.

  12. Coherent control of polarized neutron interferometry

    E-print Network

    Abutaleb, Mohamed Osama

    2012-01-01

    In this thesis, we describe two sets of experiments using a single crystal neutron interferometer. First, we explore applications of quantum information processing (QIP) to magnetic materials characterization using polarized ...

  13. Controlling attosecond electron dynamics by phase-stabilized polarization gating

    E-print Network

    Loss, Daniel

    LETTERS Controlling attosecond electron dynamics by phase-stabilized polarization gating I. J. SOLA attosecond pulse is generated. Here we demonstrate that by modulating the polarization of a carrier confines the extreme-ultraviolet emission to an isolated attosecond pulse with a broad and tunable

  14. A Quasioptical Vector Interferometer for Polarization Control

    NASA Technical Reports Server (NTRS)

    Chuss, David T.; Wollack, Edward J.; Moseley, Harvey S.; Novak, Giles

    2005-01-01

    We present a mathematical description of a Quasioptical Vector Interferometer (QVI), a device that maps an input polarization state to an output polarization state by introducing a phase delay between two linear orthogonal components of the input polarization. The advantages of such a device over a spinning wave-plate modulator for measuring astronomical polarization in the far-infrared through millimeter are: 1. The use of small, linear motions eliminates the need for cryogenic rotational bearings, 2. The phase flexibility allows measurement of Stokes V as well as Q and U, and 3. The QVI allows for both multi-wavelength and broadband modulation. We suggest two implementations of this device as an astronomical polarization modulator. The first involves two such modulators placed in series. By adjusting the two phase delays, it is possible to use such a modulator to measure Stokes Q, U, and V for passbands that are not too large. Conversely, a single QVI may be used to measure Q and V independent of frequency. In this implementation, Stokes U must be measured by rotating the instrument. We conclude this paper by presenting initial laboratory results.

  15. Coherent optical control of polarization with a critical metasurface

    NASA Astrophysics Data System (ADS)

    Kang, Ming; Chong, Y. D.

    2015-10-01

    We present a mechanism by which a metamaterial surface, or metasurface, can act as an ideal phase-controlled rotatable linear polarizer. Using coupled-mode theory and the idea of coherent perfect absorption into auxiliary polarization channels, we show how the losses and near-field couplings on the metasurface can be balanced so that, with equal-power linearly polarized beams incident on each side, varying the relative phase rotates the polarization angles of the output beams while maintaining zero ellipticity. The system can be described by a non-Hermitian effective Hamiltonian which is parity-time (P T ) symmetric, although there is no actual gain present; perfect polarization conversion occurs at the eigenfrequencies of this Hamiltonian, and the polarization rotating behavior occurs at the critical point of its P T -breaking transition.

  16. Electrically pumped semiconductor laser with monolithic control of circular polarization.

    PubMed

    Rauter, Patrick; Lin, Jiao; Genevet, Patrice; Khanna, Suraj P; Lachab, Mohammad; Giles Davies, A; Linfield, Edmund H; Capasso, Federico

    2014-12-30

    We demonstrate surface emission of terahertz (THz) frequency radiation from a monolithic quantum cascade laser with built-in control over the degree of circular polarization by "fishbone" gratings composed of orthogonally oriented aperture antennas. Different grating concepts for circularly polarized emission are introduced along with the presentation of simulations and experimental results. Fifth-order gratings achieve a degree of circular polarization of up to 86% within a 12°-wide core region of their emission lobes in the far field. For devices based on an alternative transverse grating design, degrees of circular polarization as high as 98% are demonstrated for selected far-field regions of the outcoupled THz radiation and within a collection half-angle of about 6°. Potential and limitations of integrated antenna gratings for polarization-controlled emission are discussed. PMID:25512515

  17. Electrically pumped semiconductor laser with monolithic control of circular polarization

    PubMed Central

    Rauter, Patrick; Lin, Jiao; Genevet, Patrice; Khanna, Suraj P.; Lachab, Mohammad; Giles Davies, A.; Linfield, Edmund H.; Capasso, Federico

    2014-01-01

    We demonstrate surface emission of terahertz (THz) frequency radiation from a monolithic quantum cascade laser with built-in control over the degree of circular polarization by “fishbone” gratings composed of orthogonally oriented aperture antennas. Different grating concepts for circularly polarized emission are introduced along with the presentation of simulations and experimental results. Fifth-order gratings achieve a degree of circular polarization of up to 86% within a 12°-wide core region of their emission lobes in the far field. For devices based on an alternative transverse grating design, degrees of circular polarization as high as 98% are demonstrated for selected far-field regions of the outcoupled THz radiation and within a collection half-angle of about 6°. Potential and limitations of integrated antenna gratings for polarization-controlled emission are discussed. PMID:25512515

  18. Single frequency stable VCSEL as a compact source for interferometry and vibrometry

    SciTech Connect

    Dudzik, Grzegorz; Rzepka, Janusz

    2010-05-28

    Developing an innovative PS-DAVLL (Polarization Switching DAVLL) method of frequency stabilization, which used a ferroelectric liquid crystal cell as quarter wave plate, rubidium cell and developed ultra-stable current source, allowed to obtain a frequency stability of 10{sup -9}(frequency reproducibility of 1,2centre dot10{sup -8}) and reductions in external dimensions of laser source. The total power consumption is only 1,5 Watt. Because stabilization method used in the frequency standard is insensitive to vibration, the semiconductor laser interferometer was built for measuring range over one meter, which can also be used in industry for the accurate measurement of displacements with an accuracy of 1[mum/m]. Measurements of the VCSEL laser parameters are important from the standpoint of its use in laser interferometry or vibrometry, like narrow emission line DELTAnu{sub FWHM} = 70[MHz] equivalent of this laser type and stability of linear polarization of VCSEL laser. The undoubted advantage of the constructed laser source is the lack of mode-hopping effect during continuous work of VCSEL.

  19. Polar auxin transport: controlling where and how much

    NASA Technical Reports Server (NTRS)

    Muday, G. K.; DeLong, A.; Brown, C. S. (Principal Investigator)

    2001-01-01

    Auxin is transported through plant tissues, moving from cell to cell in a unique polar manner. Polar auxin transport controls important growth and developmental processes in higher plants. Recent studies have identified several proteins that mediate polar auxin transport and have shown that some of these proteins are asymmetrically localized, paving the way for studies of the mechanisms that regulate auxin transport. New data indicate that reversible protein phosphorylation can control the amount of auxin transport, whereas protein secretion through Golgi-derived vesicles and interactions with the actin cytoskeleton might regulate the localization of auxin efflux complexes.

  20. Self-Sustained Ultrafast Pulsation in Coupled VCSELs

    NASA Technical Reports Server (NTRS)

    Ning, Cun-Zheng

    2001-01-01

    High frequency, narrow-band self-pulsating operation is demonstrated in two coupled vertical-cavity surface-emitting lasers (VCSELs). The coupled VCSELs provide an ideal source for high-repetition rate (over 40 GHz), sinusoidal-like modulated laser source with Gaussian-like near- and far-field profiles. We also show that the frequency of the modulation can be tuned by the inter-VCSEL separation or by DC-bias level.

  1. Experimental observation of localized structures in medium size VCSELs.

    PubMed

    Averlant, Etienne; Tlidi, Mustapha; Thienpont, Hugo; Ackemann, Thorsten; Panajotov, Krassimir

    2014-01-13

    We report experimental evidence of spontaneous formation of localized structures in a 80 ?m diameter Vertical-Cavity Surface-Emitting Laser (VCSEL) biased above the lasing threshold and under optical injection. Such localized structures are bistable with the injected beam power and the VCSEL current. We experimentally investigate the formation of localized structures for different detunings between the injected beam and the VCSEL, and different injection beam waists. PMID:24515036

  2. Comparison of Techniques for Bonding VCSELs Directly to Ics

    SciTech Connect

    Choquette, K.D.; Geib, K.M.; Hayes, E.M. Wilmsen, C.W.; Hou, H.Q.; Pu, R.

    1999-03-26

    This paper reports the successful bonding of 8 x 8 and 4 x 4 VCSEL arrays to Si CMOS and GaAs MESFET integrated circuits and to GaAs substrates. Three different bonding techniques are demonstrated and their electrical, optical and mechanical characteristics are compared. All three techniques remove the substrate from the VCSEL wafer, leaving individual VCSELs bonded directly to locations within the integrated circuit.

  3. High-speed VCSEL-based optical interconnects

    NASA Astrophysics Data System (ADS)

    Ishak, Waguih S.

    2001-11-01

    Vertical Cavity Surface Emitting Lasers (VCSEL) have made significant inroads into commercial realization especially in the area of data communications. Single VCSEL devices are key components in Gb Ethernet Transceivers. A multi-element VCSEL array is the key enabling technology for high-speed multi Gb/s parallel optical interconnect modules. In 1996, several companies introduced a new generation of fiber optic products based VCSEL technology such as multimode fiber transceivers for the ANSI Fiber Channel and Gigabit Ethernet IEEE 802.3 standards. VCSELs offer unique advantages over its edge-emitting counterparts in several areas. These include low-cost (LED-like) manufacturability, low current operation and array integrability. As data rates continue to increase, VCSELs offer the advantage of being able to provide the highest modulation bandwidth per milliamp of modulation current. Currently, most of the VCSEL-based products use short (780 - 980 nm) wavelength lasers. However, significant research efforts are taking place at universities and industrial research labs around the world to develop reliable, manufacturable and high-power long (1300 - 1550 nm) wavelength VCSELs. These lasers will allow longer (several km) transmission distances and will help alleviate some of the eye-safety issues. Perhaps, the most important advantage of VCSELs is the ability to form two-dimensional arrays much easier than in the case of edge-emitting lasers. These arrays (single and two-dimensional) will allow a whole new family of applications, specifically in very high-speed computer and switch interconnects.

  4. GaAs/AlOx high-contrast grating mirrors for mid-infrared VCSELs

    NASA Astrophysics Data System (ADS)

    Almuneau, G.; Laaroussi, Y.; Chevallier, C.; Genty, F.; Fressengeas, N. s.; Cerutti, L.; Gauthier-Lafaye, Olivier

    2015-02-01

    Mid-infrared Vertical cavity surface emitting lasers (MIR-VCSEL) are very attractive compact sources for spectroscopic measurements above 2?m, relevant for molecules sensing in various application domains. A long-standing issue for long wavelength VCSEL is the large structure thickness affecting the laser properties, added for the MIR to the tricky technological implementation of the antimonide alloys system. In this paper, we propose a new geometry for MIR-VCSEL including both a lateral confinement by an oxide aperture, and a high-contrast sub-wavelength grating mirror (HCG mirror) formed by the high contrast combination AIOx/GaAs in place of GaSb/A|AsSb top Bragg reflector. In addition to drastically simplifying the vertical stack, HCG mirror allows to control through its design the beam properties. The robust design of the HCG has been ensured by an original method of optimization based on particle swarm optimization algorithm combined with an anti-optimization one, thus allowing large error tolerance for the nano-fabrication. Oxide-based electro-optical confinement has been adapted to mid-infrared lasers, byusing a metamorphic approach with (Al) GaAs layer directly epitaxially grown on the GaSb-based VCSEL bottom structure. This approach combines the advantages of the will-controlled oxidation of AlAs layer and the efficient gain media of Sb-based for mid-infrared emission. We finally present the results obtained on electrically pumped mid-IR-VCSELs structures, for which we included oxide aperturing for lateral confinement and HCG as high reflectivity output mirrors, both based on AlxOy/GaAs heterostructures.

  5. VCSEL fault location apparatus and method

    DOEpatents

    Keeler, Gordon A. (Albuquerque, NM); Serkland, Darwin K. (Albuquerque, NM)

    2007-05-15

    An apparatus for locating a fault within an optical fiber is disclosed. The apparatus, which can be formed as a part of a fiber-optic transmitter or as a stand-alone instrument, utilizes a vertical-cavity surface-emitting laser (VCSEL) to generate a test pulse of light which is coupled into an optical fiber under test. The VCSEL is subsequently reconfigured by changing a bias voltage thereto and is used as a resonant-cavity photodetector (RCPD) to detect a portion of the test light pulse which is reflected or scattered from any fault within the optical fiber. A time interval .DELTA.t between an instant in time when the test light pulse is generated and the time the reflected or scattered portion is detected can then be used to determine the location of the fault within the optical fiber.

  6. Stokes vector characterization of the polarization behavior of vertical-cavity surface-emitting lasers.

    PubMed

    Molitor, Andreas; Hartmann, Sébastien; Elsässer, Wolfgang

    2012-11-15

    We demonstrate that a full polarization analysis in terms of the Stokes vector parameters is necessary to determine the polarization state of light emitted by vertical-cavity surface-emitting lasers (VCSELs). For three selected representative VCSEL devices, we measured the injection current dependence of the three Stokes parameters and compared these results with linearly selected polarization P-I curves, clearly demonstrating that a complete polarization analysis is required to unveil the full polarization behavior. PMID:23164918

  7. Integrated-optic polarization controllers based on polymer waveguide

    NASA Astrophysics Data System (ADS)

    Kim, Jun-Whee; Park, Su-Hyun; Chu, Woo-Sung; Oh, Min-Cheol

    2013-03-01

    Polarization controllers are demonstrated by integrated polymer waveguide technology. The integrated-optic polarization controllers consist of three birefringence modulators and 45°-inclined quarter-wave plates inserted between them. The birefringence modulator by incorporating highly birefringent polymer material exhibits the difference in phase retardation for TE and TM guided modes in proportion to the heating power. Thin-film quarter-wave plates are fabricated by using a reactive mesogen, and inserted between the birefringence modulators to produce static phase retardation and polarization coupling. By applying a triangular AC signal to one birefringence modulator and a DC signal to another, general polarization conversion covering the entire surface of the Poincaré sphere is demonstrated.

  8. Polarization control in ridge-waveguide-laser diodes

    SciTech Connect

    Amann, M.

    1987-04-20

    The polarization dependence of the gain/current relation and threshold current of quasi-index-guided laser diodes is analyzed for the case of lambda = 1.3 ..mu..m InGaAsP-InP ridge-waveguide lasers. Thereby it is shown that three different regimes for the stripe width and the lateral effective index discontinuity can be distinguished where one modal polarization (TE or TM) predominates. The significance of this finding on laser design and polarization control is discussed, and a comparison is performed on experimental results.

  9. Optical design aspects of VCSEL-Solder-Joints Christiane Gimkiewicz

    E-print Network

    Jahns, Jürgen

    Optical design aspects of VCSEL-Solder-Joints Christiane Gimkiewicz We consider a multichip module the optical interconnection length s: The optical spacing z0, which is equal to the thickness of the solder-Space Optical Interconnects and VCSEL-Solder-Joints, Microsystem Techn. Vol. 7 (2001) 249­255. [2] Sauer, F

  10. October 2, 2009 Radiation-Hardness of VCSEL/PIN

    E-print Network

    Gan, K. K.

    optical power for 6 arrays irradiated await return of arrays to Ohio State for annealing/characterization.20 Irradiated 2 arrays or several single channel devices for each type Hamamatsu devices have low bandwidth-Ionizing Energy Loss (NIEL) K.K. Gan #12;RD09 4 850 nm VCSEL Irradiation 2006-7: "~2 VCSEL arrays were

  11. Antimonide-based approaches for long-wavelength VCSELs

    SciTech Connect

    Klem, J.F.; Blum, O.; Lear, K.

    1998-08-01

    Mixed arsenide/antimonide materials have unique properties which make them potentially valuable for use in VCSELs operating at wavelengths longer than 1 {micro}m. The authors present their progress in applying these materials to VCSEL designs for 1--1.55 {micro}m.

  12. Ultra-sensitive immunoassay using VCSEL detection system

    E-print Network

    Cunningham, Brian

    emitting laser (VCSEL) as the new detection system [2]. The biosensor (molecular binding surface) used here-Hasnain, J.E. Foley, R. Beatty, P. Li and B.T. Cunningham Highly sensitive protein characterisation on a new label-free biosensor system is reported. The system consists of a VCSEL, a plastic guided mode resonant

  13. Full-field interferometric confocal microscopy using a VCSEL array

    E-print Network

    Cao, Hui

    an interferometric confocal microscope using an array of 1200 vertical cavity surface emitting lasers (VCSELs sectioning as a scanning confocal microscope without moving parts, while the high power of the VCSEL array (5 for fluorescence imaging, it has the potential for high-speed, large-area reflectance imaging with confocal

  14. Prediction and evaluation of infant failures of oxide VCSELs

    NASA Astrophysics Data System (ADS)

    Lee, Sook-Hui; Pyun, Su-Hyun; Kim, Hee Dae; Shin, Hyun Kuk; Hwang, In-Kag

    2014-12-01

    Vertical-cavity surface-emitting lasers (VCSELs) with oxide layers introduced for modal property control are relatively weak against reliability-related damage. We propose and demonstrate a method of detecting potential damage without running a long-term burn-in test. For two damage mechanisms, chemical etching and electrostatic discharge, we found that an exceptional increase in the ideality factor ( Id V/d I) is closely related to potential damage of the device that will eventually lead to failure in the following burn-in test. The extent and the origin of the damage could also be identified by using the heights and locations of the bumps in the ideality factor curves.

  15. Cavity structures for low loss oxide-confined VCSELs

    SciTech Connect

    Choquette, K.D.; Hadley, G.R.; Chow, W.W.; Hou, H.Q.; Geib, K.M.; Hammons, B.E.; Mathes, D.; Hull, R.

    1997-05-01

    The authors examine the threshold characteristics of selectively oxidized VCSELs as a function of the number, thickness, and placement of the buried oxide apertures. The threshold current density for small area VCSELs is shown to increase with the number of oxide apertures in the cavity due to increased optical loss, while the threshold current density for broad area VCSELs decreases with increasing number of apertures due to more uniform current injection. Reductions of the threshold gain and optical loss are achieved for small area VCSELs using thin oxide apertures which are displaced longitudinally away from te optical cavity. They show that the optical loss can be sufficiently reduced to allow lasing in VCSELs with aperture area as small as 0.25 {micro}m{sup 2}.

  16. K.K. Gan Pixel Opto-Link Workshop 1 Summary of VCSEL Problems and

    E-print Network

    Gan, K. K.

    K.K. Gan Pixel Opto-Link Workshop 1 Summary of VCSEL Problems and Opto-Board Production Plan Nov 30-Link Workshop 2 Outline Chronology of VCSEL problems Summary of VCSEL problems/contradictions Opto-board production schedule #12;K.K. Gan Pixel Opto-Link Workshop 3 First Hint of Problem 2002: an VCSEL array

  17. Generation of polarization-resolved wideband unpredictability-enhanced chaotic signals based on vertical-cavity surface-emitting lasers subject to chaotic optical injection.

    PubMed

    Chen, Jian-Jun; Wu, Zheng-Mao; Tang, Xi; Deng, Tao; Fan, Li; Zhong, Zhu-Qiang; Xia, Guang-Qiong

    2015-03-23

    A system framework is proposed and analyzed for generating polarization-resolved wideband unpredictability-enhanced chaotic signals based on a slave vertical-cavity surface-emitting laser (S-VCSEL) driven by an injected optical chaos signal from a master VCSEL (M-VCSEL) under optical feedback. After calculating the time series outputs from the M-VCSEL under optical feedback and the S-VCSEL under chaotic optical injection by using the spin-flip model (SFM), the unpredictability degree (UD) is evaluated by permutation entropy (PE), and the bandwidth of the polarization-resolved outputs from the M-VCSEL and S-VCSEL are numerically investigated. The results show that, under suitable parameters, both the bandwidth and UD of two polarization components (PCs) outputs from the S-VCSEL can be enhanced significantly compared with that of the driving chaotic signals output from the M-VCSEL. By simulating the influences of the feedback and injection parameters on the bandwidth and UD of the polarization-resolved outputs from S-VCSEL, related operating parameters can be optimized. PMID:25837062

  18. Polarization characteristics, control, and modulation of vertical-cavity surface emitting lasers

    SciTech Connect

    Choquette, K.D.; Lear, K.L.; Schneider, R.P. Jr.; Figiel, J.J.; Kilcoyne, S.P.; Hagerott-Crawford, M.; Zolper, J.C.; Leibenguth, R.E.

    1995-03-01

    The gain-dependent polarization properties of vertical-cavity surface emitting lasers and methods for polarization control and modulation are discussed. The partitioning of power between the two orthogonal eigen polarizations is shown to depend upon the relative spectral alignment of the nondegenerate polarization cavity resonances with the laser gain spectrum. A dominant polarization can thus be maintained by employing a blue-shifted offset of the peak laser gain relative to the cavity resonance wavelength. Alternatively, the polarization can be controlled through use of anisotropic transverse cavity geometries. The orthogonal eigen polarizations are also shown to enable polarization modulation. By exploiting polarization switching transitions in cruciform lasers, polarization modulation of the fundamental mode up to 50 MHz is demonstrated. At lower modulation frequencies, complementary digital polarized output or frequency doubling of the polarized output is obtained. Control and manipulation of vertical-cavity laser polarization may prove valuable for present and future applications.

  19. Multiplexed gas spectroscopy using tunable VCSELs

    SciTech Connect

    Bond, T; Bond, S; McCarrick, J; Zumstein, J; Chang, A; Moran, B; Benett, W J

    2012-04-10

    Detection and identification of gas species using tunable laser diode laser absorption spectroscopy has been performed using vertical cavity surface emitting lasers (VCSEL). Two detection methods are compared: direct absorbance and wavelength modulation spectroscopy (WMS). In the first, the output of a DC-based laser is directly monitored to detect for any quench at the targeted specie wavelength. In the latter, the emission wavelength of the laser is modulated by applying a sinusoidal component on the drive current of frequency {omega}, and measuring the harmonics component (2{omega}) of the photo-detected current. This method shows a better sensitivity measured as signal to noise ratio, and is less susceptible to interference effects such as scattering or fouling. Gas detection was initially performed at room temperature and atmospheric conditions using VCSELs of emission wavelength 763 nm for oxygen and 1392 nm for water, scanning over a range of approximately 10 nm, sufficient to cover 5-10 gas specific absorption lines that enable identification and quantization of gas composition. The amplitude and frequency modulation parameters were optimized for each detected gas species, by performing two dimensional sweeps for both tuning current and either amplitude or frequency, respectively. We found that the highest detected signal is observed for a wavelength modulation amplitude equal to the width of the gas absorbance lines, in good agreement with theoretical calculations, and for modulation frequencies below the time response of the lasers (<50KHz). In conclusion, we will discuss limit of detection studies and further implementation and packaging of VCSELs in diode arrays for continuous and simultaneous monitoring of multiple species in gaseous mixtures.

  20. Controllable valley polarization using graphene multiple topological line defects

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Song, Juntao; Li, Yuxian; Liu, Ying; Sun, Qing-feng

    2013-05-01

    The electron transport of different conical valleys is investigated in graphene with extended line defects. Intriguingly, the electron with a definite incident angle can be completely modulated into one conical valley by a resonator which consists of several paralleling line defects. The related incident angle can be controlled easily by tuning the parameters of the resonator. Therefore, a controllable 100% valley polarization, as well as the detection of the valley polarization, can be realized conveniently by tuning the number of line defects and the distance between two nearest-neighboring line defects. This fascinating finding opens a way to realize the valley polarization by line defects. With the advancement of experimental technologies, this resonator is promising to be realized and thus plays a key role in graphene valleytronics.

  1. Polarization Control of Electron Tunneling into Ferroelectric Surfaces

    SciTech Connect

    Maksymovych, Petro; Jesse, Stephen; Yu, Pu; Ramesh, R.; Baddorf, Arthur P; Kalinin, Sergei V

    2009-01-01

    We demonstrate a highly reproducible control of local electron transport through a ferroelectric oxide via its spontaneous polarization. Electrons are injected from the tip of an atomic force microscope into a thin film of lead-zirconate titanate, Pb(Zr0.2Ti0.8)O3, in the regime of electron tunneling assisted by a high electric field (Fowler-Nordheim tunneling). The tunneling current exhibits a pronounced hysteresis with abrupt switching events that coincide, within experimental resolution, with the local switching of ferroelectric polarization. The large spontaneous polarization of the PZT film results in up to 500-fold amplification of the tunneling current upon ferroelectric switching. The magnitude of the effect is subject to electrostatic control via ferroelectric switching, suggesting possible applications in ultrahigh-density data storage and spintronics.

  2. High-speed and scalable high-power VCSEL arrays and their applications

    NASA Astrophysics Data System (ADS)

    Warren, Mial E.; Carson, Richard F.; Joseph, John R.; Wilcox, Thomas; Dacha, Preethi; Abell, David J.; Otis, Kirk J.

    2015-03-01

    A unique architecture for two-dimensional arrays of VCSELs that allow for simultaneous high-power output and highbandwidth modulation has been developed for a variety of applications. The arrays use integrated micro-lenses for beam shaping and control, and to enable incoherent beam combining to make compact, high-brightness sources with low coherence noise. The fabrication and performance of the laser arrays are reviewed and sample applications are discussed.

  3. Novel Configurable Logic Block Architecture Exploiting Controllable-Polarity Transistors

    E-print Network

    De Micheli, Giovanni

    to reduce the access resistances at the source and drain interfaces of Metal-Oxide-Semiconductor Field switch. Controllable-polarity devices can be realized in diverse technol- ogies, such as silicon reconfigurable logic blocks. A. Ultra-Fine Grain Reconfigurable Logic We first review the behavior

  4. Independent control of polar and azimuthal anchoring.

    PubMed

    Anquetil-Deck, C; Cleaver, D J; Bramble, J P; Atherton, T J

    2013-07-01

    Monte Carlo simulation, experiment, and continuum theory are used to examine the anchoring exhibited by a nematic liquid crystal at a patterned substrate comprising a periodic array of rectangles that, respectively, promote vertical and planar alignment. It is shown that the easy axis and effective anchoring energy promoted by such surfaces can be readily controlled by adjusting the design of the pattern. The calculations reveal rich behavior: for strong anchoring, as exhibited by the simulated system, for rectangle ratios ?2 the nematic aligns in the direction of the long edge of the rectangles, the azimuthal anchoring coefficient changing with pattern shape. In weak anchoring scenarios, however, including our experimental systems, preferential anchoring is degenerate between the two rectangle diagonals. Bistability between diagonally aligned and edge-aligned arrangement is predicted for intermediate combinations of anchoring coefficient and system length scale. PMID:23944468

  5. Widely tunable telecom MEMS-VCSEL for terahertz photomixing.

    PubMed

    Haidar, Mohammad Tanvir; Preu, Sascha; Paul, Sujoy; Gierl, Christian; Cesar, Julijan; Emsia, Ali; Küppers, Franko

    2015-10-01

    We report frequency-tunable terahertz (THz) generation with a photomixer driven by an ultra-broadband tunable micro-electro-mechanical system vertical-cavity surface-emitting laser (MEMS-VCSEL) and a fixed-wavelength VCSEL, as well as a tunable MEMS-VCSEL mixed with a distributed feedback (DFB) diode. A total frequency span of 3.4 THz is covered in direct detection mode and 3.23 THz in the homodyne mode. The tuning range is solely limited by the dynamic range of the photomixers and the Schottky diode/photoconductor used in the experiment. PMID:26421548

  6. Athermal and widely tunable VCSEL with bimorph micromachined mirror.

    PubMed

    Nakahama, Masanori; Sakaguchi, Takahiro; Matustani, Akihiro; Koyama, Fumio

    2014-09-01

    We demonstrate an athermal and electrostatically-tunable 850 nm-band MEMS VCSEL for the first time. The thermal wavelength drift is compensated by the thermal actuation of a cantilever-suspended mirror with a bimorph effect. At the same time, the resonant wavelength can be continuously tuned by electro-static force as a voltage is applied in the cantilever structure. A continuous wavelength tuning of 10 nm is obtained with a low thermal wavelength drift, which is 10 times smaller than that of conventional VCSELs. Our athermal and tunable VCSELs enable us to reduce the channel spacing in course wavelength division multiplexing optical interconnects even under uncooled operations. PMID:25321525

  7. Coherent control of optical polarization effects in metamaterials

    PubMed Central

    Mousavi, Seyedmohammad A.; Plum, Eric; Shi, Jinhui; Zheludev, Nikolay I.

    2015-01-01

    Processing of photonic information usually relies on electronics. Aiming to avoid the conversion between photonic and electronic signals, modulation of light with light based on optical nonlinearity has become a major research field and coherent optical effects on the nanoscale are emerging as new means of handling and distributing signals. Here we demonstrate that in slabs of linear material of sub-wavelength thickness optical manifestations of birefringence and optical activity (linear and circular birefringence and dichroism) can be controlled by a wave coherent with the wave probing the polarization effect. We demonstrate this in proof-of-principle experiments for chiral and anisotropic microwave metamaterials, where we show that the large parameter space of polarization characteristics may be accessed at will by coherent control. Such control can be exerted at arbitrarily low intensities, thus arguably allowing for fast handling of electromagnetic signals without facing thermal management and energy challenges. PMID:25755071

  8. New applications boost VCSEL quantities: recent developments at Philips

    NASA Astrophysics Data System (ADS)

    Grabherr, Martin

    2015-03-01

    Besides the mature and steadily growing datacom market for which VCSELs are key components in Transceivers, Active Optical Cables (AOC), Mid Board Optical Modules (MBOM) or Embedded Optical Modules (EOM), VCSELs have proven to be key components also for other volume applications. Laser mice emerged 2004, just after the burst of the dotcom bubble and the related downturn in the Datacom industry, and dominated the shipped quantities for some years, accompanied by various smaller applications like atomic clock, oxygen sensing, encoders, and many more. Over the past years, two other major applications came into focus: optical interconnects in high performance computers or datacenters and smart sensors for mobile devices. In addition, VCSELs are penetrating into more and more power applications, primarily for illumination or IR heating. We present recent developments in technology, products, and addressed market segments that will have a major impact on the VCSEL industry.

  9. 3D finite element simulation of optical modes in VCSELs

    E-print Network

    Rozova, M; Zschiedrich, L; Schmidt, F; Burger, S

    2011-01-01

    We present a finite element method (FEM) solver for computation of optical resonance modes in VCSELs. We perform a convergence study and demonstrate that high accuracies for 3D setups can be attained on standard computers.

  10. Mode partition noise characterization of 25 Gb/s VCSELs

    NASA Astrophysics Data System (ADS)

    Murty, M. V. Ramana; Cunningham, David; Giovane, Laura; Wang, Jingyi; Feng, Zheng-Wen; Fanning, Thomas R.

    2015-03-01

    Mode partition noise (MPN) can become the dominant limitation in 850 nm VCSEL-based multi-mode fiber (MMF) links at high data rates. Fluctuations in the partition of energy between the transverse modes of the VCSEL combined with the chromatic dispersion in the fiber leads to intensity noise at the receiver. The impact of MPN on non-equalized and equalized links has been studied with a numerical model of the VCSEL and MMF. The MPN in 25 Gb/s VCSELs has been investigated by examining noise in individual mode groups isolated using a thin film Fabry-Perot filter. The measured k factor below 0.15 should enable links significantly longer than 100 m at 25 Gb/s and higher data rates.

  11. Quantum phase gate and controlled entanglement with polar molecules

    SciTech Connect

    Charron, Eric; Keller, Arne; Atabek, Osman; Milman, Perola

    2007-03-15

    We propose an alternative scenario for the generation of entanglement between rotational quantum states of two polar molecules. This entanglement arises from dipole-dipole interaction, and is controlled by a sequence of laser pulses simultaneously exciting both molecules. We study the efficiency of the process, and discuss possible experimental implementations with cold molecules trapped in optical lattices or in solid matrices. Finally, various entanglement detection procedures are presented, and their suitability for these two physical situations is analyzed.

  12. Polarization-controlling dual-band absorption metamaterial

    NASA Astrophysics Data System (ADS)

    Tuong Pham, Van; Vu, Dinh Lam; Park, Jin Woo; Lee, YoungPak

    2013-09-01

    We investigated sandwich structure of the conventional absorber metamaterials to expand the study on dual-band absorption in our previous work (2013 Appl. Phys. Lett. 102 081122). The advantages of the artificial structuring of plasmonic resonators or ‘meta-atoms’ were exploited to gradually enhance/degrade the absorption peaks by polarization angle of electromagnetic wave. By reshaping the rings at the font of slab, dual- or single-peak absorption is controlled. The absorber is demonstrated in the GHz region.

  13. February 24, 2009 Radiation-Hardness of VCSEL/PIN

    E-print Network

    Gan, K. K.

    February 24, 2009 Radiation-Hardness of VCSEL/PIN W. Fernando, K.K. Gan, H.P. Kagan, R.D. Kass, J Introduction Radiation hardness of PINs Radiation hardness of VCSELs Summary #12;K.K. Gan ATLAS Upgrade with 50% safety factor #12;K.K. Gan ATLAS Upgrade Week 5 K.K. Gan 5 Radiation-Hardness of Silicon PIN

  14. Spectrally resolved imaging of the transverse modes in multimode VCSELs

    NASA Astrophysics Data System (ADS)

    Misak, Stephen M.; Dugmore, Dan G.; Middleton, Kirsten A.; Hale, Evan R.; Farner, Kelly R.; Choquette, Kent D.; Leisher, Paul O.

    2015-03-01

    Vertical-cavity surface-emitting lasers (VCSELs) enable a range of applications such as data transmission, trace sensing, atomic clocks, and optical mice. For many of these applications, the output power and beam quality are both critical (i.e. high output power with good beam quality is desired). Multi-mode VCSELs offer much higher power than single-mode devices, but this comes at the expense of lower beam quality. Directly observing the resolved mode structure of multi-mode VCSELs would enable engineers to better understand the underlying physics and help them to develop multi-mode devices with improved beam quality. In this work, a low-cost, high-resolution (<3 pm) Echelle grating spectrometer system is used to map the two-dimensional VCSEL near-field emission profile. The system spectrally disperses the VCSEL beam and images it with high magnification onto a CMOS camera. The narrow spectral content of each LP mode allows direct observation of the modal content of the VCSEL.

  15. Stable polarization self-modulation in vertical-cavity surface-emitting lasers

    SciTech Connect

    Li, H.; Hohl, A.; Gavrielides, A.; Hou, H.; Choquette, K.D.

    1998-05-01

    The characteristics of polarization self-modulation in a vertical-cavity surface-emitting laser (VCSEL) were studied for frequencies up to {approx}9 GHz both experimentally and theoretically. Polarization self-modulation was obtained by rotating the linearly polarized output of the VCSEL by 90{degree} and reinjecting it into the laser. Experimentally we simultaneously recorded time traces, optical and radio-frequency spectra. We found for increasing modulation frequencies that the output characteristics changed from square-wave to sinusoidal and the VCSEL system assumed new polarization eigenstates that are different from the free-running VCSEL eigenstates. We modeled polarization self-modulation as an interband process and found a good qualitative agreement between our experimental and numerical results. {copyright} {ital 1998 American Institute of Physics.}

  16. Piezotronic Effect in Polarity-Controlled GaN Nanowires.

    PubMed

    Zhao, Zhenfu; Pu, Xiong; Han, Changbao; Du, Chunhua; Li, Linxuan; Jiang, Chunyan; Hu, Weiguo; Wang, Zhong Lin

    2015-08-25

    Using high-quality and polarity-controlled GaN nanowires (NWs), we studied the piezotronic effect in crystal orientation defined wurtzite structures. By applying a normal compressive force on c-plane GaN NWs with an atomic force microscopy tip, the Schottky barrier between the Pt tip and GaN can be effectively tuned by the piezotronic effect. In contrast, the normal compressive force cannot change the electron transport characteristics in m-plane GaN NWs whose piezoelectric polarization axis is turned in the transverse direction. This observation provided solid evidence for clarifying the difference between the piezotronic effect and the piezoresistive effect. We further demonstrated a high sensitivity of the m-plane GaN piezotronic transistor to collect the transverse force. The integration of c-plane GaN and m-plane GaN indicates an overall response to an external force in any direction. PMID:26256533

  17. Recent advances in MEMS-VCSELs for high performance structural and functional SS-OCT imaging

    E-print Network

    Jayaraman, V.

    Since the first demonstration of swept source optical coherence tomography (SS-OCT) imaging using widely tunable micro-electromechanical systems vertical cavity surface-emitting lasers (MEMS-VCSELs) in 2011, VCSEL-based ...

  18. Room-temperature optically-pumped GaSb quantum well based VCSEL monolithically

    E-print Network

    Jalali. Bahram

    Room-temperature optically-pumped GaSb quantum well based VCSEL monolithically grown on Si (100.P. Haines, L.R. Dawson and D.L. Huffaker Monolithic vertical cavity surface emitting lasers (VCSELs) on Si%) without the use of a buffer layer. Presented are VCSEL lasing spectra, light-in against light-out curves

  19. Air cooling of a VCSEL diode array on quartz Christiane Gimkiewicz, Jurgen Jahns

    E-print Network

    Jahns, Jürgen

    Air cooling of a VCSEL diode array on quartz Christiane Gimkiewicz, J¨urgen Jahns Planar optics in combination with VCSEL arrays has been suggested as a viable approach to overcome the bottleneck of electronic [2]. An 8 × 8 vertical cavity surface emitting laser diode (VCSEL) array was flipchip bonded onto

  20. Automatical adjustment of optimal VCSEL sources bias points U. Lohmann, H. Knuppertz, J. Jahns

    E-print Network

    Jahns, Jürgen

    Automatical adjustment of optimal VCSEL sources bias points U. Lohmann, H. Knuppertz, J. Jahns bias-, modulation current and threshold point of the VCSEL has a strong bearing on the optical performance of the laser modul. For example the lower deviation of the VCSEL threshold point creates signal

  1. Study of the Radiation-Hardness of VCSEL and PIN , W. Fernandoa

    E-print Network

    Gan, K. K.

    Study of the Radiation-Hardness of VCSEL and PIN K.K. Gana , B. Abic , W. Fernandoa , H.P. Kagana), an upgraded LHC with ten times higher luminosity. We study the radiation-hardness of VCSELs (Vertical in the data transmission upgrade. The optical power of VCSEL arrays decreases significantly after

  2. FIRST DEMONSTRATION OF MODULATION VIA FIELD-INDUCED CHARGE-SEPARATION IN VCSELS

    E-print Network

    Rodwell, Mark J. W.

    FIRST DEMONSTRATION OF MODULATION VIA FIELD-INDUCED CHARGE-SEPARATION IN VCSELS Chin-Han Lin , Yan-induced charge-separation lasers (FICSLs) in VCSEL form were designed and fabricated. The new gain modulation-efficiency diode VCSELs are the cornerstones for short-haul fiber links and free-space boar- to-board optical

  3. Parallel transport of biological cells using individually addressable VCSEL arrays as optical tweezers

    E-print Network

    Esener, Sadik C.

    Parallel transport of biological cells using individually addressable VCSEL arrays as optical (VCSELs) for optical trapping and active manipulation of live biological cells and microspheres. We have experimentally verified that the Laguerre­Gaussian laser mode output from the VCSEL functions just as well

  4. Microscope-integrated Micromanipulator based on Multiple VCSEL , Sanja Zlatanovic, Sadik C. Esener

    E-print Network

    Esener, Sadik C.

    Microscope-integrated Micromanipulator based on Multiple VCSEL Traps Bing Shao , Sanja Zlatanovic Dr., La Jolla, CA 92093-0408 ABSTRACT The compactness of VCSELs (Vertical Cavity Surface Emitting research, optical trapping of live biological cells and microspheres based on VCSEL array has been realized

  5. Polarization control of absorption of virtual dressed states in helium

    NASA Astrophysics Data System (ADS)

    Reduzzi, Maurizio; Hummert, Johan; Dubrouil, Antoine; Calegari, Francesca; Nisoli, Mauro; Frassetto, Fabio; Poletto, Luca; Chen, Shaohao; Wu, Mengxi; Gaarde, Mette B.; Schafer, Kenneth; Sansone, Giuseppe

    2015-09-01

    The extreme ultraviolet absorption spectrum of an atom is strongly modified in the presence of a synchronized intense infrared field. In this work we demonstrate control of the absorption properties of helium atoms dressed by an infrared pulse by changing the relative polarization of the infrared and extreme ultraviolet fields. Light-induced features associated with the dressed 1 s 2 s , 1 s 3 s , and 1 s 3 d states, referred to as 2 s+ , 3 s± , and 3 d± light-induced states, are shown to be strongly modified or even eliminated when the relative polarization is rotated. The experimental results agree well with calculations based on the solution of the time-dependent Schrödinger equation using a restricted excitation model that allows efficient treatment of the three-dimensional problem. We also present an analysis of the light-induced states based on Floquet theory, which allows for a simple explanation of their properties. Our results open a new route to creating controllable superpositions of dipole allowed and nondipole allowed states in atoms and molecules.

  6. Polarization-Independent Silicon Metadevices for Efficient Optical Wavefront Control.

    PubMed

    Chong, Katie E; Staude, Isabelle; James, Anthony; Dominguez, Jason; Liu, Sheng; Campione, Salvatore; Subramania, Ganapathi S; Luk, Ting S; Decker, Manuel; Neshev, Dragomir N; Brener, Igal; Kivshar, Yuri S

    2015-08-12

    We experimentally demonstrate a functional silicon metadevice at telecom wavelengths that can efficiently control the wavefront of optical beams by imprinting a spatially varying transmittance phase independent of the polarization of the incident beam. Near-unity transmittance efficiency and close to 0-2? phase coverage are enabled by utilizing the localized electric and magnetic Mie-type resonances of low-loss silicon nanoparticles tailored to behave as electromagnetically dual-symmetric scatterers. We apply this concept to realize a metadevice that converts a Gaussian beam into a vortex beam. The required spatial distribution of transmittance phases is achieved by a variation of the lattice spacing as a single geometric control parameter. PMID:26192100

  7. Wink-controlled polarization-switched telescopic contact lenses.

    PubMed

    Schuster, Glenn M; Arianpour, Ashkan; Cookson, Scott; Zhang, Arthur; Hendrik, Lee; O'Brien, Tyrone; Alvarez, Agusto; Ford, Joseph E

    2015-11-10

    We describe a wink-controlled hands-free switching system for eye-borne telescopic vision, based on a previously tested fixed-magnification telescope embedded within scleral contact lenses. Here we integrate orthogonal polarizers into the contact lens covering the F/9.1 refractive 1× and F/9.6 catadioptric 2.8× vision paths, to allow switching via external liquid crystal shutters. We provide hands-free control by an infrared wink/blink monitor, using passive retroreflectors embedded within the contact lenses. We demonstrate system operation of the self-contained switching eyewear and the modified contact lenses with a life-size human eye model with mechanical "eyelids." PMID:26560792

  8. Polarization Controlled Directional Scattering for Nanoscopic Position Sensing

    E-print Network

    Neugebauer, Martin; Bag, Ankan; Leuchs, Gerd; Banzer, Peter

    2015-01-01

    Controlling the propagation and coupling of light to sub-wavelength antennas is a crucial prerequisite for many nanoscale optical devices. Recently, the main focus of attention has been directed towards high-refractive index materials such as silicon as an integral part of the antenna design. The development is motivated by the rich spectral properties of individual high-refractive index nanoparticles, featuring magnetic and electric resonances in the visible regime, whose interference may yield remarkably strong directivity. Here, we use tightly focused radially polarized light for controlled excitation of a spherical silicon nanoantenna. The resultant emission can be highly directional, depending on the antenna's position relative to the focus. This approach finds application as a novel position sensing technique, a discipline, which is of paramount importance in modern nanometrology, because of its special role in super-resolution microscopy. We yield a lateral resolution in the Angstrom regime.

  9. Free space ranging based on a chaotic long-wavelength VCSEL with optical feedback

    NASA Astrophysics Data System (ADS)

    Quirce, Ana; Perez, Pablo; Valle, Angel; Pesquera, Luis; Esquivias, Ignacio; Panajotov, Krassimir; Thienpont, Hugo

    2015-03-01

    Chaotic Lidar systems (CLIDAR) are used for high-resolution ranging. They are based on the correlation of a chaotic signal waveform with the signal that is reflected back from the target. We report a novel CLIDAR system based on the autocorrelation of the signal obtained by the superposition of the chaotic signal waveform and the signal that is reflected from the target. A simplified set-up with just one detector is required in contrast to the two detectors used in standard CLIDAR systems. Our experimental results are obtained with a 1550-nm vertical-cavity surface-emitting laser (VCSEL) with chaotic dynamics due to optical feedback. Our CLIDAR system provides an autocorrelation function with several sharp minima. The position of the target is obtained from the location of those minima. A theoretical analysis of the CLIDAR system is also presented. A rate equation model for the polarization of a VCSEL subject to optical feedback is the basis for the simulation of the CLIDAR system. A comparison between our theoretical and experimental results is performed, resulting in a good agreement in the chaotic signal but in a different sign of the CLIDAR signal.

  10. attitude control design for the solar polar orbit radio telesope

    NASA Astrophysics Data System (ADS)

    Gao, D.; Zheng, J.

    This paper studies the attitude dynamics and control of the Solar Polar Orbit Radio Telescope SPORT The SPORT which consists of one parent satellite and eight tethered satellites runs around the Sun in a polar orbit The parent satellite locates at the mass center of the constellation and tethered satellites which are tied with the parent satellite through a non-electric rope rotate around the parent satellite It is also supposed that the parent satellite and all tethered satellites are in a plane when the constellation works begin figure htbp centerline includegraphics width 3 85in height 2 38in 75271331 6a6eb71057 doc1 eps label fig1 end figure Fig 1 the SPORT constellation Firstly this paper gives the dynamic equations of the tethered satellite and the parent satellite From the dynamic characteristic of the tethered satellite we then find that the roll axis is coupled with the yaw axis The control torque of the roll axis can control the yaw angle But the control torque of the roll axis and pitch axis provided by the tether is very small it can not meet the accuracy requirement of the yaw angle In order to improve the attitude pointing accuracy of the tethered satellite a gradient pole is set in the negative orientation of the yaw axis The gradient pole can improve not only the attitude accuracy of roll angle and pitch angle but also that of the yaw angle indirectly As to the dynamic characteristic of the parent satellite the roll axis is coupled with the pitch axis due to the spinning angular velocity At the same

  11. Comparison of fabrication approaches for selectively oxidized VCSEL arrays

    SciTech Connect

    GEIB,KENT M.; CHOQUETTE,KENT D.; ALLERMAN,ANDREW A.; BRIGGS,RONALD D.; HINDI,JANA JO

    2000-04-18

    The impressive performance improvements of laterally oxidized VCSELs come at the expense of increased fabrication complexity for 2-dimensional arrays. Since the epitaxial layers to be wet-thermally oxidized must be exposed, non-planarity can be an issue. This is particularly important in that electrical contact to both the anode and cathode of the diode must be brought out to a package. They have investigated four fabrication sequences suitable for the fabrication of 2-dimensional VCSEL arrays. These techniques include: mesa etched polymer planarized, mesa etched bridge contacted, mesa etched oxide isolated (where the electrical trace is isolated from the substrate during the oxidation) and oxide/implant isolation (oxidation through small via holes) all of which result in VCSELs with outstanding performance. The suitability of these processes for manufacturing are assessed relative to oxidation uniformity, device capacitance, and structural ruggedness for packaging.

  12. Temperature characteristic of 808nm VCSELs with large aperture

    NASA Astrophysics Data System (ADS)

    Feng, Yuan; Feng, Dawei; Hao, Yongqin; Wang, Yong; Yan, Changling; Lu, Peng; Li, Yang

    2015-03-01

    In order to study the output characteristics of 808nm vertical cavity surface emitting laser(VCSEL) with large aperture at different temperature, 808nm VCSEL with 500?m emitting diameter are fabricated with Reticular Electrode Structure(RES). Lasing wavelength, optical power and the threshold current are measured by changing the temperature of heat sink. And an output power of 0.42W is achieved at 1.3A at room temperature under continuous wave operation. The central wavelength is 803.32nm, and the full width at half maximum is 0.16nm, the temperature shift is 0.06nm/°, the thermal resistance is 0.098°/mW. The testing results show that 808nm VCSEL with large aperture is good temperature characteristic.

  13. Exploring the influence of boundary shapes on emission angular distributions and polarization states of broad-area vertical-cavity surface-emitting lasers.

    PubMed

    Yu, Y T; Tuan, P H; Huang, K F; Chen, Y F

    2014-11-01

    We design the stadium-shaped and rectangular vertical-cavity surface-emitting lasers (VCSELs) to investigate the influence of boundary shapes on the emission angular distributions and polarization states. For the stadium-shaped VCSELs, the emission angular distribution prefers to be almost omnidirectional because the lasing mode with purely scarred structure is seldom to be excited. On the contrary, the rectangular VCSELs usually generate dominant lasing modes with the morphology of quasi-periodic linear ridges, which can make emission angular distribution to be concentrated on the certain direction. From the polarization-resolved light-current curves, the stadium-shaped VCSEL is quite prone to exhibit numerous abrupt changes (kinks) associated with polarization switching with increasing current, whereas for rectangular VCSEL there is no conspicuous kink to be seen during a wide range of current changing from near to far above lasing threshold. PMID:25401843

  14. Full-field interferometric confocal microscopy using a VCSEL array

    PubMed Central

    Redding, Brandon; Bromberg, Yaron; Choma, Michael A.; Cao, Hui

    2014-01-01

    We present an interferometric confocal microscope using an array of 1200 VCSELs coupled to a multimode fiber. Spatial coherence gating provides ~18,000 continuous virtual pinholes allowing an entire en face plane to be imaged in a snapshot. This approach maintains the same optical sectioning as a scanning confocal microscope without moving parts, while the high power of the VCSEL array (~5 mW per laser) enables high-speed image acquisition with integration times as short as 100 µs. Interferometric detection also recovers the phase of the image, enabling quantitative phase measurements and improving the contrast when imaging phase objects. PMID:25078199

  15. Study of the Radiation Hardness of Vcsel and Pin Arrays

    E-print Network

    Gan, K K

    2009-01-01

    The silicon trackers of the ATLAS experiment at LHC (CERN) use optical links for data transmission. VCSEL arrays operating at 850 nm are used to transmit optical signals while PIN arrays are used to convert the optical signals into electrical signals. We investigate the feasibility of using the devices at the Super LHC (SLHC). We irradiated VCSEL and GaAs PIN arrays from three vendors and silicon PIN arrays from one vendor. All arrays can be operated up to the SLHC dosage except the GaAs PIN arrays which have very low responsivities after irradiation and hence are probably not suitable for the SLHC application.

  16. Full-field interferometric confocal microscopy using a VCSEL array.

    PubMed

    Redding, Brandon; Bromberg, Yaron; Choma, Michael A; Cao, Hui

    2014-08-01

    We present an interferometric confocal microscope using an array of 1200 vertical cavity surface emitting lasers (VCSELs) coupled to a multimode fiber. Spatial coherence gating provides ~18,000 continuous virtual pinholes, allowing an entire en face plane to be imaged in a snapshot. This approach maintains the same optical sectioning as a scanning confocal microscope without moving parts, while the high power of the VCSEL array (?5??mW per laser) enables high-speed image acquisition with integration times as short as 100 ?s. Interferometric detection also recovers the phase of the image, enabling quantitative phase measurements and improving the contrast when imaging phase objects. PMID:25078199

  17. Study of the Radiation Hardness of Vcsel and Pin Arrays

    E-print Network

    K. K. Gan

    2009-01-06

    The silicon trackers of the ATLAS experiment at LHC (CERN) use optical links for data transmission. VCSEL arrays operating at 850 nm are used to transmit optical signals while PIN arrays are used to convert the optical signals into electrical signals. We investigate the feasibility of using the devices at the Super LHC (SLHC). We irradiated VCSEL and GaAs PIN arrays from three vendors and silicon PIN arrays from one vendor. All arrays can be operated up to the SLHC dosage except the GaAs PIN arrays which have very low responsivities after irradiation and hence are probably not suitable for the SLHC application.

  18. Size dependence of selectively oxidized VCSEL transverse mode structure

    SciTech Connect

    Hegarty, S.P.; Huyet, G.; McInerney, J.G. |; Choquette, K.D.; Hou, H.Q.; Geib, K.M.

    1998-05-01

    The performance of vertical cavity surface emitting lasers (VCSELs) has improved greatly in recent years. Much of this improvement can be attributed to the use of native oxide layers within the laser structure, providing both electrical and optical transverse confinement. Understanding this optical confinement will be vital for the future realization of yet smaller lasers with ultralow threshold currents. Here the authors report the spectral and modal properties of small (0.5 {micro}m to 5 {micro}m current aperture) VCSELs and identify Joule heating as a dominant effect in the resonator properties of the smallest lasers.

  19. High-power VCSEL arrays for consumer electronics

    NASA Astrophysics Data System (ADS)

    Graham, Luke A.; Chen, Hao; Cruel, Jonathan; Guenter, James; Hawkins, Bobby; Hawthorne, Bobby; Kelly, David Q.; Melgar, Alirio; Martinez, Mario; Shaw, Edward; Tatum, Jim A.

    2015-03-01

    Finisar has developed a line of high power, high efficiency VCSEL arrays. They are fabricated at 860nm as traditional P side up top emitting devices, leveraging Finisar's existing VCSEL fab and test processes for low cost, high volume capability. A thermal camera is used to accurately measure temperature profiles across the arrays at a variety of operating conditions and further allowing development of a full reliability model. The arrays are shown to demonstrate wear out reliability suitable for a wide range of applications. Typical 1/e^2 beam divergence is near 16 degrees under CW operating conditions at peak wall plug efficiency, narrowing further under pulsed drive conditions.

  20. Thermal resistance of VCSEL's bonded to integrated circuits

    SciTech Connect

    Pu, R.; Wilmsen, C.W.; Geib, K.M.; Choquette, K.D.

    1999-12-01

    The thermal resistance of vertical-cavity surface-emitting lasers (VCSEL's) flip chip bonded to GaAs substrates and CMOS integrated circuits has been measured. The measurements on GaAs show that if the bonding is done properly, the bonding does not add significantly to the thermal resistance. However, the SiO{sub 2} under the CMOS bonding pad can double the thermal resistance unless measures are taken to improve the thermal conductance of these layers. Finite element simulations indicate that the thermal resistance of bonded VCSEL's increases rapidly as the solder bond size and the aperture size decrease below {approximately}10 {micro}m.

  1. Interference of Coherent Polariton Beams in Microcavities: Polarization-Controlled Optical Gates

    SciTech Connect

    Leyder, C.; Romanelli, M.; Giacobino, E.; Bramati, A.; Liew, T. C. H.; Kavokin, A. V.; Shelykh, I. A.; Karr, J. Ph.

    2007-11-09

    We demonstrate, theoretically and experimentally, a polarization-controlled optical gate based on a degenerate polariton-polariton scattering process occurring in semiconductor microcavities. Because of the interference between coherent polaritons, this process is observed in the case of polaritons generated from two collinearly polarized coherent pump beams. On the contrary, if the beams are cross polarized, the scattering is suppressed.

  2. Control of cell polarity and mitotic spindle positioning in animal cells

    E-print Network

    Ahringe, Julie

    Control of cell polarity and mitotic spindle positioning in animal cells Julie Ahringer Cell polarity is an essential feature of many animal cells. It is critical for epithelial formation and function the establishment of polarity and subsequent spindle positioning in many animal cells. Microtubules and conserved

  3. A 10 Gbps WDM transport system based on VCSELs to VCSELs injection locked technique and LEAF transport

    NASA Astrophysics Data System (ADS)

    Lu, Hai-Han; Tsai, Wen-Shing; Chen, Ching-Yi; Peng, Hsiang-Chun

    2004-11-01

    A 10 Gbps wavelength-division-multiplexing (WDM) transport system based on vertical cavity surface emitting lasers (VCSELs) to VCSELs injection locked technique and large effective area fiber (LEAF) transport is proposed and demonstrated. Improved bit error rate (BER) performance was observed over a 50 km LEAF transport, attributed to the laser bandwidth enhancement and chromatic dispersion reduction. This demonstrated that such a WDM transport system is very attractive for the 10 Gbps backbone applications, which can inter-operate with high-speed optical communication networks.

  4. Compactly packaged monolithic four-wavelength VCSEL array with 100-GHz wavelength spacing for future-proof mobile fronthaul transport.

    PubMed

    Lee, Eun-Gu; Mun, Sil-Gu; Lee, Sang Soo; Lee, Jyung Chan; Lee, Jong Hyun

    2015-01-12

    We report a cost-effective transmitter optical sub-assembly using a monolithic four-wavelength vertical-cavity surface-emitting laser (VCSEL) array with 100-GHz wavelength spacing for future-proof mobile fronthaul transport using the data rate of common public radio interface option 6. The wavelength spacing is achieved using selectively etched cavity control layers and fine current adjustment. The differences in operating current and output power for maintaining the wavelength spacing of four VCSELs are <1.4 mA and <1 dB, respectively. Stable operation performance without mode hopping is observed, and error-free transmission under direct modulation is demonstrated over a 20-km single-mode fiber without any dispersion-compensation techniques. PMID:25835675

  5. Numerical Investigation of Leaky-Mode Coupling in VCSELs

    SciTech Connect

    Hadley, G. R.

    1997-12-31

    We investigate various aspects of leaky-mode coupling behavior in Vertical-Cavity Surface-Emitting Lasers (VCSELs) using a 2D finite difference model to simulate two coupled pixels. Phase-locking is shown to occur in a manner consistent with previous simple models.

  6. Uniformity and performance of selectively oxidized VCSEL arrays

    SciTech Connect

    Geib, K.M.; Choquette, K.D.; Hou, H.Q.; Hammons, B.E.

    1998-01-01

    The authors report the uniformity characteristics of low threshold 1,060 nm and high power 850 nm 8 x 8 individually addressable oxide-confined VCSEL arrays. Uniformity of lasing thresholds and operating characteristics are described, as well as thermal issues for 2-dimensional laser arrays.

  7. A Signaling Network Induced by ?2 Integrin Controls the Polarization of Lytic Granulesin Cytotoxic Cells

    PubMed Central

    Zhang, Minggang; March, Michael E.; Lane, William S.; Long, Eric O.

    2014-01-01

    Cytotoxic lymphocyte skill target cells by polarized release of the content of perforin-containing granules. In natural killer cells, the binding of ?2 integrin to its ligand ICAM-1 is sufficient to promote not only adhesion but also lytic granule polarization. This provided a unique opportunity to study polarization in the absence of degranulation, and ?2 integrin signaling independently of inside-out signals from other receptors. Using an unbiased proteomics approach we identified a signaling network centered on an integrin-linked kinase (ILK)–Pyk2–Paxillin core that was required for granule polarization. Downstream of ILK, the highly conserved Cdc42–Par6 signaling pathway that controls cell polarity was activated and required for granule polarization. These results delineate two connected signaling networks induced upon ?2 integrin engagement alone, which are integrated to control polarization of the microtubule organizing center and associated lytic granules toward the site of contact with target cells during cellular cytotoxicity. PMID:25292215

  8. Direction controllable linearly polarized laser from a dye-doped cholesteric liquid crystal

    E-print Network

    Wu, Shin-Tson

    Direction controllable linearly polarized laser from a dye-doped cholesteric liquid crystal Ying demonstrate a direction controllable linearly polarized laser from a dye-doped cholesteric liquid crystal (CLC codes: (230.3720) Liquid crystal devices; (160, 3710) Materials References and links 1. V. I. Kopp, Z. Q

  9. Direction controllable linearly polarized laser from a dye-doped cholesteric liquid crystal

    E-print Network

    Wu, Shin-Tson

    Direction controllable linearly polarized laser from a dye-doped cholesteric liquid crystal Ying demonstrate a direction controllable linearly polarized laser from a dye-doped cholesteric liquid crystal (CLC codes: (230.3720) Liquid-crystal devices, (160, 3710) Materials References and links 1. V. I. Kopp, Z. Q

  10. Laser polarization and phase control of up-conversion fluorescence in rare-earth ions

    PubMed Central

    Yao, Yunhua; Zhang, Shian; Zhang, Hui; Ding, Jingxin; Jia, Tianqing; Qiu, Jianrong; Sun, Zhenrong

    2014-01-01

    We theoretically and experimentally demonstrate the up-conversion fluorescence control via resonance-mediated two-photon absorption in rare-earth ions by varying both the laser polarization and phase. We show that both the laser polarization and phase can control the up-conversion fluorescence, and the up-conversion fluorescence intensity is decreased when the laser polarization changes from linear through elliptical to circular. We also show that the laser polarization will affect the control efficiency of the up-conversion fluorescence by varying the laser phase, and the circular polarization will reduce the control efficiency. Furthermore, we suggest that the control efficiency by varying the laser polarization and the effect of the laser polarization on the control efficiency by varying the laser phase can be artificially manipulated by controlling the laser spectral bandwidth. This optical control method opens a new opportunity to control the up-conversion fluorescence of rare-earth ions, which may have significant impact on the related applications of rare-earth ions. PMID:25465401

  11. Active inductor shunt peaking in high-speed VCSEL driver design

    E-print Network

    Futian Liang; Datao Gong; Suen Hou; Chonghan Liu; Tiankuan Liu; Da-Shung Su; Ping-Kun Teng; Annie Xiang; Jingbo Ye; Ge Jin

    2013-06-04

    An all transistor active inductor shunt peaking structure has been used in a prototype of 8-Gbps high-speed VCSEL driver which is designed for the optical link in ATLAS liquid Argon calorimeter upgrade. The VCSEL driver is fabricated in a commercial 0.25-um Silicon-on-Sapphire (SoS) CMOS process for radiation tolerant purpose. The all transistor active inductor shunt peaking is used to overcome the bandwidth limitation from the CMOS process. The peaking structure has the same peaking effect as the passive one, but takes a small area, does not need linear resistors and can overcome the process variation by adjust the peaking strength via an external control. The design has been tapped out, and the prototype has been proofed by the preliminary electrical test results and bit error ratio test results. The driver achieves 8-Gbps data rate as simulated with the peaking. We present the all transistor active inductor shunt peaking structure, simulation and test results in this paper.

  12. Active inductor shunt peaking in high-speed VCSEL driver design

    E-print Network

    Liang, Futian; Hou, Suen; Liu, Chonghan; Liu, Tiankuan; Su, Da-Shung; Teng, Ping-Kun; Xiang, Annie; Ye, Jingbo; Jin, Ge

    2013-01-01

    An all transistor active inductor shunt peaking structure has been used in a prototype of 8-Gbps high-speed VCSEL driver which is designed for the optical link in ATLAS liquid Argon calorimeter upgrade. The VCSEL driver is fabricated in a commercial 0.25-um Silicon-on-Sapphire (SoS) CMOS process for radiation tolerant purpose. The all transistor active inductor shunt peaking is used to overcome the bandwidth limitation from the CMOS process. The peaking structure has the same peaking effect as the passive one, but takes a small area, does not need linear resistors and can overcome the process variation by adjust the peaking strength via an external control. The design has been tapped out, and the prototype has been proofed by the preliminary electrical test results and bit error ratio test results. The driver achieves 8-Gbps data rate as simulated with the peaking. We present the all transistor active inductor shunt peaking structure, simulation and test results in this paper.

  13. Dielectric metasurfaces for complete control of phase and polarization with subwavelength spatial resolution and high transmission.

    PubMed

    Arbabi, Amir; Horie, Yu; Bagheri, Mahmood; Faraon, Andrei

    2015-11-01

    Metasurfaces are planar structures that locally modify the polarization, phase and amplitude of light in reflection or transmission, thus enabling lithographically patterned flat optical components with functionalities controlled by design. Transmissive metasurfaces are especially important, as most optical systems used in practice operate in transmission. Several types of transmissive metasurface have been realized, but with either low transmission efficiencies or limited control over polarization and phase. Here, we show a metasurface platform based on high-contrast dielectric elliptical nanoposts that provides complete control of polarization and phase with subwavelength spatial resolution and an experimentally measured efficiency ranging from 72% to 97%, depending on the exact design. Such complete control enables the realization of most free-space transmissive optical elements such as lenses, phase plates, wave plates, polarizers, beamsplitters, as well as polarization-switchable phase holograms and arbitrary vector beam generators using the same metamaterial platform. PMID:26322944

  14. Dielectric metasurfaces for complete control of phase and polarization with subwavelength spatial resolution and high transmission

    NASA Astrophysics Data System (ADS)

    Arbabi, Amir; Horie, Yu; Bagheri, Mahmood; Faraon, Andrei

    2015-11-01

    Metasurfaces are planar structures that locally modify the polarization, phase and amplitude of light in reflection or transmission, thus enabling lithographically patterned flat optical components with functionalities controlled by design. Transmissive metasurfaces are especially important, as most optical systems used in practice operate in transmission. Several types of transmissive metasurface have been realized, but with either low transmission efficiencies or limited control over polarization and phase. Here, we show a metasurface platform based on high-contrast dielectric elliptical nanoposts that provides complete control of polarization and phase with subwavelength spatial resolution and an experimentally measured efficiency ranging from 72% to 97%, depending on the exact design. Such complete control enables the realization of most free-space transmissive optical elements such as lenses, phase plates, wave plates, polarizers, beamsplitters, as well as polarization-switchable phase holograms and arbitrary vector beam generators using the same metamaterial platform.

  15. K.K. Gan Group B Meeting 1 VCSEL/PIN irradiation in pre-qualification

    E-print Network

    Gan, K. K.

    K.K. Gan Group B Meeting 1 VCSEL/PIN irradiation in pre-qualification: ~2 devices-qualify Optowell (GaAs) and Hamamatsu (Si)? VCSEL/PIN irradiation with large sample ~20 devices/vendor VCSEL: AOC 10 Gb/s, AOC 5 Gb/s, Optowell (2.5 Gb/s) GaAs PIN: try to order 12-channel Hamamatsu bare

  16. Concepts for long wavelength VCSELs above 2 ?m

    NASA Astrophysics Data System (ADS)

    Sprengel, Stephan; Amann, Markus-Christian

    2015-03-01

    We present different concepts for long wavelength buried tunnel junction VCSELs for the spectroscopically important range above 2 ?m. This includes GaSb-based laser using GaInAsSb quantum wells, InP-based lasers with V-shaped quantum wells and InP-based lasers using type-II quantum wells. For InP-based devices, emission wavelengths up to 2.36 ?m are presented, with single-mode output powers of roughly 500 ?W and side-mode suppression ratios of more than 30 dB. GaSb-based VCSELs are presented with single-mode emission at 2.6 ?m, a side-mode suppression ratio of more than 20 dB and a peak output power of 400 ?W.

  17. Optimization of electrically tunable VCSEL with intracavity nematic liquid crystal.

    PubMed

    Belmonte, Carlos; Frasunkiewicz, Leszek; Czyszanowski, Tomasz; Thienpont, Hugo; Beeckman, Jeroen; Neyts, Kristiaan; Panajotov, Krassimir

    2015-06-15

    We optimize the wavelength tuning range of a Vertical-Cavity Surface-Emitting Laser with an intracavity layer of nematic Liquid Crystal (LC-VCSEL) lasing around 1.3 ?m. The tunability is obtained by applying voltage to the liquid crystal layer, which esentially is to vary the refractive index from the extraordinary to the ordinary. We achieve 71.6 nm continuous tuning (without mode hopping) with liquid crystal thickness of about 3.2 ?m. We investigate the impact of ambient temperature on the LC-VCSEL tuning range and show that mode-hop tuning can be achieved in the temperature range from -10°C to 50°C where the LC is in nematic phase. PMID:26193549

  18. Study of the Radiation-Hardness of VCSEL and PIN

    E-print Network

    Gan, K K; Fernando, W; Kagan, H P; Kass, R D; Lebbai, M R M; Merritt, H; Moore, J R; Nagarkar, A; Rizatdinova, F; Skubic, P L; Smith, D S; Strang, M

    2009-01-01

    The silicon trackers of the ATLAS experiment at the Large Hadron Collider (LHC) at CERN (Geneva) use optical links for data transmission. An upgrade of the trackers is planned for the Super LHC (SLHC), an upgraded LHC with ten times higher luminosity. We study the radiation-hardness of VCSELs (Vertical-Cavity Surface-Emitting Laser) and GaAs and silicon PINs using 24 GeV/c protons at CERN for possible application in the data transmission upgrade. The optical power of VCSEL arrays decreases significantly after the irradiation but can be partially annealed with high drive currents. The responsivities of the PIN diodes also decrease significantly after irradiation, but can be recovered by operating at higher bias voltage. This provides a simple mechanism to recover from the radiation damage.

  19. Free-Space Optical Interconnect Employing VCSEL Diodes

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Savich, Gregory R.; Torres, Heidi

    2009-01-01

    Sensor signal processing is widely used on aircraft and spacecraft. The scheme employs multiple input/output nodes for data acquisition and CPU (central processing unit) nodes for data processing. To connect 110 nodes and CPU nodes, scalable interconnections such as backplanes are desired because the number of nodes depends on requirements of each mission. An optical backplane consisting of vertical-cavity surface-emitting lasers (VCSELs), VCSEL drivers, photodetectors, and transimpedance amplifiers is the preferred approach since it can handle several hundred megabits per second data throughput.The next generation of satellite-borne systems will require transceivers and processors that can handle several Gb/s of data. Optical interconnects have been praised for both their speed and functionality with hopes that light can relieve the electrical bottleneck predicted for the near future. Optoelectronic interconnects provide a factor of ten improvement over electrical interconnects.

  20. Solar illumination control of ionospheric outflow above polar cap arcs

    NASA Astrophysics Data System (ADS)

    Maes, L.; Maggiolo, R.; De Keyser, J.; Dandouras, I.; Fear, R. C.; Fontaine, D.; Haaland, S.

    2015-03-01

    We measure the flux density, composition, and energy of outflowing ions above the polar cap, accelerated by quasi-static electric fields parallel to the magnetic field and associated with polar cap arcs, using Cluster. Mapping the spacecraft position to its ionospheric foot point, we analyze the dependence of these parameters on the solar zenith angle (SZA). We find a clear transition at SZA between ˜94° and ˜107°, with the O+ flux higher above the sunlit ionosphere. This dependence on the illumination of the local ionosphere indicates that significant O+ upflow occurs locally above the polar ionosphere. The same is found for H+, but to a lesser extent. This effect can result in a seasonal variation of the total ion upflow from the polar ionosphere. Furthermore, we show that low-magnitude field-aligned potential drops are preferentially observed above the sunlit ionosphere, suggesting a feedback effect of ionospheric conductivity.

  1. Independent control of differently-polarized waves using anisotropic gradient-index metamaterials

    PubMed Central

    Ma, Hui Feng; Wang, Gui Zhen; Jiang, Wei Xiang; Cui, Tie Jun

    2014-01-01

    We propose a kind of anisotropic gradient-index (GRIN) metamaterials, which can be used to control differently-polarized waves independently. We show that two three- dimensional (3D) planar lenses made of such anisotropic GRIN metamaterials are able to make arbitrary beam deflections for the vertical (or horizontal) polarization but have no response to the horizontal (or vertical) polarization. Then the vertically- and horizontally-polarized waves are separated and controlled independently to deflect to arbitrarily different directions by designing the anisotropic GRIN planar lenses. We make experimental verifications of the lenses using such a special metamaterial, which has both electric and magnetic responses simultaneously to reach approximately equal permittivity and permeability. Hence excellent impedance matching is obtained between the GRIN planar lenses and the air. The measurement results demonstrate good performance on the independent controls of differently-polarized waves, as observed in the numerical simulations. PMID:25231412

  2. Baseline scheme for polarization preservation and control in the MEIC ion complex

    SciTech Connect

    Derbenev, Yaroslav S.; Lin, Fanglei; Morozov, Vasiliy; Zhang, Yuhong; Kondratenko, Anatoliy; Kondratenko, M A; Filatov, Yury

    2015-09-01

    The scheme for preservation and control of the ion polarization in the Medium-energy Electron-Ion Collider (MEIC) has been under active development in recent years. The figure-8 configuration of the ion rings provides a unique capability to control the polarization of any ion species including deuterons by means of "weak" solenoids rotating the particle spins by small angles. Insertion of "weak" solenoids into the magnetic lattices of the booster and collider rings solves the problem of polarization preservation during acceleration of the ion beam. Universal 3D spin rotators designed on the basis of "weak" solenoids allow one to obtain any polarization orientation at an interaction point of MEIC. This paper presents the baseline scheme for polarization preservation and control in the MEIC ion complex.

  3. Rapid Switching and Modulation by use of Coupled VCSELs

    NASA Technical Reports Server (NTRS)

    Goorjian, Peter M.; Ning, Cun-Zhen

    2004-01-01

    Devices incorporating coupled vertical-cavity surface-emitting lasers (VCSELs) have been proposed as means to effect unprecedentedly rapid modulation and/or switching of light beams in advanced optical communication and information-processing systems. A basic device according to the proposal would comprise two or more VCSELs (1) positioned so close to each other that they are coupled and (2) connected to a current source that biases them at a steady current above the threshold current for lasing. The operation of VCSELs under the conditions stated above has been simulated computationally with an algorithm that solves an approximation of the Maxwell-Bloch equations. (These are nonlinear coupled partial differential equations that model the relevant aspects of the physics of semiconductor lasers.) The results of the simulations show that the intensities of the beams oscillate, out of phase relative to each other, at a frequency that is typically of the order of tens of gigahertz. In particular, one simulation was performed for two coupled VCSELs, each having a circular aperture 5.6 microns in diameter, operating at a wavelength of 980 nm. The results of the simulation showed that the intensities of the two beams oscillated in opposite phase (see Figure 1) at a frequency of 42 GHz. In the far field, the beams were found to be separated by an angle of approx.=8deg. The intensities of the beams were also found to oscillate in the near field, 90deg out of phase with the oscillation in the far field. Figure 2 depicts a simple near-field switching device in which an assembly of microlenses would couple the two oscillating beams to two receivers.

  4. Multi-species gas detection with long-wavelength VCSEL

    NASA Astrophysics Data System (ADS)

    Lytkine, Alexandre; Jaeger, Wolfgang; Tulip, John

    2004-12-01

    A long-wavelength VCSEL has been used for the first time for multi-species gas detection and for trace gas sensing. The VCSEL with a buried tunnel junction (VERTILAS, Germany) was capable of covering a spectral range of 7 nm or 28 cm-1 (central wavelength at 1576.3 nm) with the laser temperature and injection current varied between 0-50 °C and 0.5-5 mA respectively. The pressure of CO:CO2=3:2 gas mixtures buffered with N2 (N2 content 0 - 90 %) was varied from 1 mBar up to 1 Bar. To avoid a non-linear dynamic tuning, the combination of a direct injection current with a saw-tooth waveform was used to sweep the laser frequency across absorption lines. A LabVIEW-based computer code was developed for multi-species gas analysis in time domain. Absorption spectra were averaged over 102-103 laser scans. It has been shown that a cross interference from all collisional partners should be taken into account for accurate multi-component gas detection. A concentration of 600 ppm of CO2 in atmospheric air (fractional absorption ~ 10-4) was detected with laser output power of 120 uW. Long-wavelength VCSELs can be used both for multi-species gas detection in a wide range of pressures and for trace gas monitoring.

  5. Depth-encoded all-fiber swept source polarization sensitive OCT

    PubMed Central

    Wang, Zhao; Lee, Hsiang-Chieh; Ahsen, Osman Oguz; Lee, ByungKun; Choi, WooJhon; Potsaid, Benjamin; Liu, Jonathan; Jayaraman, Vijaysekhar; Cable, Alex; Kraus, Martin F.; Liang, Kaicheng; Hornegger, Joachim; Fujimoto, James G.

    2014-01-01

    Polarization sensitive optical coherence tomography (PS-OCT) is a functional extension of conventional OCT and can assess depth-resolved tissue birefringence in addition to intensity. Most existing PS-OCT systems are relatively complex and their clinical translation remains difficult. We present a simple and robust all-fiber PS-OCT system based on swept source technology and polarization depth-encoding. Polarization multiplexing was achieved using a polarization maintaining fiber. Polarization sensitive signals were detected using fiber based polarization beam splitters and polarization controllers were used to remove the polarization ambiguity. A simplified post-processing algorithm was proposed for speckle noise reduction relaxing the demand for phase stability. We demonstrated systems design for both ophthalmic and catheter-based PS-OCT. For ophthalmic imaging, we used an optical clock frequency doubling method to extend the imaging range of a commercially available short cavity light source to improve polarization depth-encoding. For catheter based imaging, we demonstrated 200 kHz PS-OCT imaging using a MEMS-tunable vertical cavity surface emitting laser (VCSEL) and a high speed micromotor imaging catheter. The system was demonstrated in human retina, finger and lip imaging, as well as ex vivo swine esophagus and cardiovascular imaging. The all-fiber PS-OCT is easier to implement and maintain compared to previous PS-OCT systems and can be more easily translated to clinical applications due to its robust design. PMID:25401008

  6. Depth-encoded all-fiber swept source polarization sensitive OCT.

    PubMed

    Wang, Zhao; Lee, Hsiang-Chieh; Ahsen, Osman Oguz; Lee, ByungKun; Choi, WooJhon; Potsaid, Benjamin; Liu, Jonathan; Jayaraman, Vijaysekhar; Cable, Alex; Kraus, Martin F; Liang, Kaicheng; Hornegger, Joachim; Fujimoto, James G

    2014-09-01

    Polarization sensitive optical coherence tomography (PS-OCT) is a functional extension of conventional OCT and can assess depth-resolved tissue birefringence in addition to intensity. Most existing PS-OCT systems are relatively complex and their clinical translation remains difficult. We present a simple and robust all-fiber PS-OCT system based on swept source technology and polarization depth-encoding. Polarization multiplexing was achieved using a polarization maintaining fiber. Polarization sensitive signals were detected using fiber based polarization beam splitters and polarization controllers were used to remove the polarization ambiguity. A simplified post-processing algorithm was proposed for speckle noise reduction relaxing the demand for phase stability. We demonstrated systems design for both ophthalmic and catheter-based PS-OCT. For ophthalmic imaging, we used an optical clock frequency doubling method to extend the imaging range of a commercially available short cavity light source to improve polarization depth-encoding. For catheter based imaging, we demonstrated 200 kHz PS-OCT imaging using a MEMS-tunable vertical cavity surface emitting laser (VCSEL) and a high speed micromotor imaging catheter. The system was demonstrated in human retina, finger and lip imaging, as well as ex vivo swine esophagus and cardiovascular imaging. The all-fiber PS-OCT is easier to implement and maintain compared to previous PS-OCT systems and can be more easily translated to clinical applications due to its robust design. PMID:25401008

  7. Demonstration of open-quantum-system optimal control in dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Sheldon, S.; Cory, D. G.

    2015-10-01

    Dynamic nuclear polarization (DNP) is used in nuclear magnetic resonance to transfer polarization from electron spins to nuclear spins. The resulting nuclear polarization enhancement can, in theory, be two or three orders of magnitude depending on the sample. In solid-state systems, however, there are competing mechanisms of DNP, which, when occurring simultaneously, reduce the net polarization enhancement of the nuclear spin. We present a simple quantum description of DNP and apply optimal control theory (OCT) with an open-quantum-system framework to design pulses that select one DNP process and suppress the others. We demonstrate experimentally an order of magnitude improvement in the DNP enhancement using OCT pulses.

  8. Demonstration of Open Quantum System Optimal Control in Dynamic Nuclear Polarization

    E-print Network

    Sarah Sheldon; David G. Cory

    2015-07-20

    Dynamic nuclear polarization (DNP) is used in nuclear magnetic resonance (NMR) to transfer polarization from electron spins to nuclear spins. The resulting nuclear polarization enhancement can, in theory, be two or three orders of magnitude depending on the sample. In solid state systems, however, there are competing mechanisms of DNP, which, when occurring simultaneously, reduce the net polarization enhancement of the nuclear spin. We present a simple quantum description of DNP and apply optimal control theory (OCT) with an open quantum system framework to design pulses that select one DNP process and suppress the others. We demonstrate experimentally an order of magnitude improvement in the DNP enhancement using OCT pulses.

  9. Plasmonic circular polarization analyzer formed by unidirectionally controlling surface plasmon propagation

    SciTech Connect

    Li, Jiaming; Wang, Jiajian; Tang, Peng; Liu, Wei; Huang, Tao; Wang, Yanqi; Lin, Feng; Fang, Zheyu; Zhu, Xing

    2015-04-20

    Analyzing the polarization of a circularly polarized light is a critical issue. We have fabricated a spiral nano-structure on the Au film by using focused ion beam etching technique. The fabricated structure can be used as a plasmonic circular polarization analyzer. By designing the relative orientation of two nano-apertures in the spiral structural unit, the propagation direction of the surface plasmon polaritons excited by circularly polarized light of opposite handedness can be controlled. Therefore, the spiral structure could be used to accurately determine the helicity of the excited circularly polarized light. Based on the results of scanning near-field optical microscopy, the obtained circular polarization extinction ratio of this structure was above 500. This structure can be used for a flexible detecting size and a very wide spectrum.

  10. Optical implementation of polarization-independent, bidirectional, nonblocking Clos network using polarization control technique in free space

    NASA Astrophysics Data System (ADS)

    Yang, Junbo; Yang, Jiankun; Li, Xiujian; Chang, Shengli; Su, Xianyu; Ping, Xu

    2011-04-01

    The clos network is one of the earliest multistage interconnection networks. Recently, it has been widely studied in parallel optical information processing systems, and there have been many efforts to develop this network. In this paper, a smart and compact Clos network, including Clos(2,3,2) and Clos(2,4,2), is proposed by using polarizing beam-splitters (PBS), phase spatial light modulators (PSLM), and mirrors. PBS features that are s-component (perpendicular to the incident plane) of the incident light beam is reflected, and the p-component (parallel to the incident plane) passes through it. According to switching logic, under control of external electrical signals, PSLM functions to control routing paths of the signal beams, i.e., the polarization of each optical signal is rotated or not rotated 90° by a programmable PSLM. This new type of configuration grants the features of less optical components, compact in structure, efficient in performance, and insensitive to polarization of signal beam. In addition, the straight, the exchange, and the broadcast functions of the basic switch element are implemented bidirectionally in free-space. Furthermore, the new optical experimental module of 2×3 and 2×4 optical switch is also presented by a cascading polarization-independent bidirectional 2×2 optical switch. Simultaneously, the routing state-table of 2×3 and 2×4 optical switch to perform all permutation output and nonblocking switch for the input signal beam, is achieved. Since the proposed optical setup consists of only optical polarization elements, it is compact in structure, and possesses a low energy loss, a high signal-to-ratio, and an available large number of optical channels. Finally, the discussions and the experimental results show that the Clos network proposed here should be helpful in the design of large-scale network matrix, and may be used in optical communication and optical information processing.

  11. New scheme for finite-retardation limitations of linear retarders with fixed axes in polarization control

    NASA Astrophysics Data System (ADS)

    Chen, Hua; Li, Mo; Liang, Wen-Ye; Wang, Dong; He, De-Yong; Wang, Shuang; Yin, Zhen-Qiang; Chen, Wei; Guo, Guang-Can; Han, Zheng-Fu

    2016-01-01

    Finite retardation ranges of linear retarders with fixed axes limit their applications in polarization control. In this work, we present a simple and efficient constraint scheme for this finite-retardation limitation. Its theoretical basis is given geometrically and mathematically. The new polarization control algorithm combines the constraint scheme and a widely-used maximum-search algorithm. Both simulations and experiments confirm the effectiveness and practicality of the proposed scheme and control algorithm. In experiments, the control system uses four cascaded linear retarders with fast axes alternately oriented at 0° and 45°. Each retarder (fiber squeezer) has a finite retardation range of 4?. For a 15-min test, the mean (maximum) polarization error angle is 0.09 (0.28) rad while stabilizing a polarization fluctuation at an average speed of 26 rad/s. Furthermore, no events of hitting retardation limits occur.

  12. Investigation of a Polarization Controller in Titanium Diffused Lithium Niobate Waveguide near 1530 nm Wavelength 

    E-print Network

    Sung, Won Ju

    2013-12-10

    Optical polarization control in Ti diffused channel waveguides onto LiNbO_(3) substrates have been investigated near 1530 nm wavelength regime by utilizing electro-optic effects of the substrate material. A device configuration composed of two...

  13. Developing an array of site-controlled pyramidal quantum dots emitting polarization-entangled photons

    SciTech Connect

    Juska, G.; Dimastrodonato, V.; Mereni, L. O.; Gocalinska, A.; Pelucchi, E.

    2013-12-04

    We present a site-controlled, highly symmetric quantum dot system with a density of at least 15 % of polarization-entangled photon emitters. Fidelity values of the entangled state as high as 0.721±0.043 were found.

  14. 1712 IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 16, NO. 7, JULY 2004 Compact Label-Free Biosensor Using VCSEL-Based

    E-print Network

    Cunningham, Brian

    Using VCSEL-Based Measurement System Carlos F. R. Mateus, Student Member, IEEE, Michael C. Y. Huang (VCSEL)-based mea- surement system for the characterization of biomolecular interac- tions. It consists of a VCSEL, a plastic guided-mode resonant filter, and two p-i-n detectors. The system has demonstrated very

  15. Lateral Carrier Injection with n-type Modulation-doped Quantum Wells in VCSELs Chin-Han Lin1

    E-print Network

    Rodwell, Mark J. W.

    Lateral Carrier Injection with n-type Modulation-doped Quantum Wells in VCSELs Chin-Han Lin1 , Yan-Separation Laser (FICSL) in a Vertical-Cavity Surface-Emitting Laser (VCSEL) embodiment. In addition to the initial lasers. In conventional diode VCSELs, carriers are typically injected into the quantum wells from

  16. Mixed media modelling and simulation of VCSEL based optical chip level interconnections U. Lohmann, H. Knuppertz, J. Jahns

    E-print Network

    Jahns, Jürgen

    Mixed media modelling and simulation of VCSEL based optical chip level interconnections U. Lohmann intrinsic laser functions and electrical functions of the com- ponents (VCSEL driver) was realized transmitter and receiver signal conversion sequence from input voltage over VCSEL injection current to optical

  17. IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 20, NO. 6, MARCH 15, 2008 443 VCSEL Optoelectronic Biosensor for Detection of

    E-print Network

    Cunningham, Brian

    IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 20, NO. 6, MARCH 15, 2008 443 VCSEL Optoelectronic diagnosis, vertical-cavity surface-emitting lasers (VCSELs). I. INTRODUCTION RAPID detection of infectious] and a tunable vertical-cavity surface- emitting laser (VCSEL)-based detection platform [6], [7]. The surface

  18. Thermal Characteristics of Thin Film VCSELs for Fully Embedded Chip-to-Chip Guided-Wave Optical Interconnection

    E-print Network

    Chen, Ray

    Thermal Characteristics of Thin Film VCSELs for Fully Embedded Chip-to-Chip Guided-Wave Optical characteristics of a thin film VCSEL are studied both theoretically and experimentally. The theoretical analysis of thermal via effects is performed to determine optimized thickness range of VCSEL for the fully embedded

  19. Multichip module with free-space optical interconnects and VCSEL-solder-joints

    E-print Network

    Jahns, Jürgen

    Multichip module with free-space optical interconnects and VCSEL-solder-joints C. Gimkiewicz, D suggest to integrate the optical emitter/detectors (VCSEL diodes) into solder balls; onto these solder emitters into solder joints connecting the optical substrate and the IC-chips. For the hybrid integration

  20. Study of a novel type of the optical modes in VCSELs

    NASA Astrophysics Data System (ADS)

    Sokolovskii, G. S.; Dudelev, V. V.; Monakhov, A. M.; Savenko, A. Yu; Blokhin, S. A.; Deryagin, A. G.; Soboleva, K. K.; Kuzmenkov, A. G.; Losev, S. N.; Luchinin, V. V.; Maleev, N. A.; Rafailov, E. U.; Sibbett, W.; Kuchinskii, V. I.

    2014-12-01

    We study novel side-emitting modes in VCSEL microcavities. These modes correspond to ?-shaped propagation along the mesa diameter, reflection from angled mesa walls and bottom Bragg reflector. We believe this study of ?-modes is important for optimization of VCSEL design for improvement of efficiency.

  1. VCSELs in the visible to IR as a light source for low light therapy

    NASA Astrophysics Data System (ADS)

    Johnson, Klein; Dummer, Matthew; Hogan, William; Steidl, Charles; Hibbs-Brenner, Mary

    2014-02-01

    VCSELs (Vertical Cavity Surface Emitting Lasers ) provide a very versatile optical source for Low Light Therapy applications. This talk will discuss performance characteristics and packaging demonstrations for VCSELs primarily operating in the 680nm and 850nm regimes. At 680nm individual VCSELs produce >10mW, while >0.35W can be provided from a 0.4mm2 emission area. Spectral width is typically 1-2nm even for a multi-mode or array device. At 850nm these numbers increase to >30mW and >0.8W. Even higher powers can be achieved under pulsed modulation, i.e. 0.55W for a 680nm VCSEL or 1.2W for an 850nm VCSEL. While we report on results achieved at 680nm and 850nm, extension to wavelengths ranging from 660nm to 1000nm is easily achieved. The packaging flexibility of VCSELs also makes them of significant interest to the Low Light Therapy community. We will report on the incorporation of VCSELs into surface mount packages, including typical LED packages such as the PLCC, or ceramic chip carriers. VCSELs in PLCC packages have been attached to flexible circuits to provide a broad area illumination. We will also report on a unique chip on board package which easily allows for the addition of optical elements such as diffusers, diffraction gratings or lenses. This package is 2mm on a side, sufficiently small for incorporation into catheters or implantation.

  2. Metrological characterization of custom-designed 894.6 nm VCSELs for miniature atomic clocks.

    PubMed

    Gruet, F; Al-Samaneh, A; Kroemer, E; Bimboes, L; Miletic, D; Affolderbach, C; Wahl, D; Boudot, R; Mileti, G; Michalzik, R

    2013-03-11

    We report on the characterization and validation of custom-designed 894.6 nm vertical-cavity surface-emitting lasers (VCSELs), for use in miniature Cs atomic clocks based on coherent population trapping (CPT). The laser relative intensity noise (RIN) is measured to be 1 × 10(-11) Hz(-1) at 10 Hz Fourier frequency, for a laser power of 700 ?W. The VCSEL frequency noise is 10(13) · f(-1) Hz(2)/Hz in the 10 Hz < f < 10(5) Hz range, which is in good agreement with the VCSEL’s measured fractional frequency instability (Allan deviation) of ? 1 × 10(-8) at 1 s, and also is consistent with the VCSEL’s typical optical linewidth of 20-25 MHz. The VCSEL bias current can be directly modulated at 4.596 GHz with a microwave power of -6 to +6 dBm to generate optical sidebands for CPT excitation. With such a VCSEL, a 1.04 kHz linewidth CPT clock resonance signal is detected in a microfabricated Cs cell filled with Ne buffer gas. These results are compatible with state-of-the-art CPT-based miniature atomic clocks exhibiting a short-term frequency instability of 2-3 × 10(-11) at ? = 1 s and few 10(-12) at ? = 10(4) s integration time.. PMID:23482148

  3. High Efficacy Green LEDs by Polarization Controlled MOVPE

    SciTech Connect

    Wetzel, Christian

    2013-03-31

    Amazing performance in GaInN/GaN based LEDs has become possible by advanced epitaxial growth on a wide variety of substrates over the last decade. An immediate push towards product development and worldwide competition for market share have effectively reduced production cost and generated substantial primary energy savings on a worldwide scale. At all times of the development, this economic pressure forced very fundamental decisions that would shape huge industrial investment. One of those major aspects is the choice of epitaxial growth substrate. The natural questions are to what extend a decision for a certain substrate will limit the ultimate performance and to what extent, the choice of a currently more expensive substrate such as native GaN could overcome any of the remaining performance limitations. Therefore, this project has set out to explore what performance characteristic could be achieved under the utilization of bulk GaN substrate. Our work was guided by the hypotheses that line defects such as threading dislocations in the active region should be avoided and the huge piezoelectric polarization needs to be attenuated – if not turned off – for higher performing LEDs, particularly in the longer wavelength green and deep green portions of the visible spectrum. At their relatively lower performance level, deep green LEDs are a stronger indicator of relative performance improvements and seem particular sensitive to the challenges at hand. The project therefore made use of recently developed non-polar and semipolar bulk GaN substrates that were made available at Kyma Technologies by crystallographic cuts from thick polar growth of GaN. This approach naturally leads to rather small pieces of substrates, cm along the long side while mm along the short one. Small size and limited volume of sample material therefore set the limits of the ensuing development work. During the course of the project we achieved green and deep green LEDs in all those crystal growth orientations: polar c-plane, non- polar a-plane, non-polar m-plane, and semipolar planes. The active region in those structures shows dramatically reduced densities of threading dislocations unless the wavelength was extended as far as 510 nm and beyond. With the appearance of such defects, the light output power dropped precipitously supporting the necessity to avoid any and all of such defects to reach the active region. Further aspects of the non-polar growth orientation proved extremely promising for the development of such structures. Chief among them is our success to achieve extremely uniform quantum wells in these various crystal orientations that prove devoid of any alloy fluctuation beyond the theoretical limit of a binominal distribution. This became very Rensselaer Wetzel DE?EE0000627 3 directly apparent in highly advanced atom probe tomography performed in collaboration at Northwestern University. Furthermore, under reduced or absence of piezoelectric polarization, green emitters in those growth geometries exhibit an unsurpassed wavelength stability over very wide excitation and drive current ranges. Such a performance had not been possible in any polar c-plane growth and now places green LEDs in terms of wavelength stability up par with typical 450 nm blue emitters. The project also incorporated enabling opportunities in the development of micro and nano- patterned substrate technologies. Originally developped as a means to enhance generated light extraction we have demonstrated that the method of nano-patterning, in contrast to micro- patterning also results in a substantial reduction of threading dislocation generation. In green LEDs, we thereby see equal contributions of enhanced light extraction and reduced defect generation to a threefold enhancement of the green light output power. These results have opened entirely new approaches for future rapid and low cost epitaxial material development by avoidance of thick defect accommodation layers. All methods developed within this project have meanwhile widely been publicized by the members o

  4. A 26-Gb/s 1.80-pJ/b CMOS-Driven Transmitter for 850-nm Common-Cathode VCSELs

    E-print Network

    Chan Carusone, Tony

    A 26-Gb/s 1.80-pJ/b CMOS-Driven Transmitter for 850-nm Common-Cathode VCSELs M. Shibata and A. Chan-CMOS driver and an 850- nm VCSEL array in a QFN package is demonstrated. The VCSEL's anode is directly; (060.2360) Fiber optics links and subsystems 1. Introduction Direct modulation of VCSEL arrays permits

  5. Controlling Aggregation in Non-Polar Asphaltene Suspensions Through Electrostatics

    NASA Astrophysics Data System (ADS)

    Hashmi, Sara; Firoozabadi, Abbas

    2012-02-01

    Asphaltenes, the most aromatic and largest molecular weight components of petroleum fluids, can undergo a liquid-liquid phase transition in conditions including highly non-polar environments. Phase separation begins with molecular association and proceeds to and through the colloidal length-scale until complete sedimentation or deposition. Non-ionic polymeric dispersants can stabilize asphaltenes at the colloidal scale in non-polar suspensions. We perform a variety of experiments which suggest that stabilization occurs by adsorption of dispersant onto the asphaltenes, truncating the progress of precipitation. In particular, dynamic light scattering (DLS) and phase-analysis light scattering (PALS) measurements indicate that electrostatic repulsion is responsible for stabilizing asphaltene colloids against further aggregation. Aggregation time increases exponentially with dispersant concentration, as expected for particles interacting through a combination of attractive dispersion forces and repulsive electrostatics. However, contrary to current understandings of electrostatic stabilization in non-polar systems, the charges in colloidal asphaltene suspensions seem to arise from the asphaltene colloids themselves rather than from dispersant micelles.

  6. The BASL polarity protein controls a MAPK signaling feedback loop in asymmetric cell division.

    PubMed

    Zhang, Ying; Wang, Pengcheng; Shao, Wanchen; Zhu, Jian-Kang; Dong, Juan

    2015-04-20

    Cell polarization is linked to fate determination during asymmetric division of plant stem cells, but the underlying molecular mechanisms remain unknown. In Arabidopsis, BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE (BASL) is polarized to control stomatal asymmetric division. A mitogen-activated protein kinase (MAPK) cascade determines terminal stomatal fate by promoting the degradation of the lineage determinant SPEECHLESS (SPCH). Here, we demonstrate that a positive-feedback loop between BASL and the MAPK pathway constitutes a polarity module at the cortex. Cortical localization of BASL requires phosphorylation mediated by MPK3/6. Phosphorylated BASL functions as a scaffold and recruits the MAPKKK YODA and MPK3/6 to spatially concentrate signaling at the cortex. Activated MPK3/6 reinforces the feedback loop by phosphorylating BASL and inhibits stomatal fate by phosphorylating SPCH. Polarization of the BASL-MAPK signaling feedback module represents a mechanism connecting cell polarity to fate differentiation during asymmetric stem cell division in plants. PMID:25843888

  7. Full control of magnetism in a manganite bilayer by ferroelectric polarization

    SciTech Connect

    Dong, Shuai; Dagotto, Elbio R

    2013-01-01

    An oxide heterostructure made of manganite bilayers and ferroelectric perovskites is predicted to lead to the full control of magnetism when switching the ferroelectric polarizations. By using asymmetric polar interfaces in the superlattices, more electrons occupy the Mn layer at the n-type interface side than at the p-type side. This charge disproportionation can be enhanced or suppressed by the ferroelectric polarization. Quantum model and density functional theory calculations reach the same conclusion: a ferromagnetic-ferrimagnetic phase transition with maximal change >90% of the total magnetization can be achieved by switching the polarization s direction. This function is robust and provides full control of the magnetization s magnitude, not only its direction, via electrical methods.

  8. Dynamic Control of the Polarization of Intense Laser Beams via Optical Wave Mixing in Plasmas

    NASA Astrophysics Data System (ADS)

    Michel, P.; Divol, L.; Turnbull, D.; Moody, J. D.

    2014-11-01

    When intense laser beams overlap in plasmas, the refractive index modulation created by the beat wave via the ponderomotive force can lead to optical wave mixing phenomena similar to those used in crystals and photorefractive materials. A new comprehensive analytical description of the modification of the polarization state of laser beams crossing at arbitrary angles in a plasma is presented. It is shown that a laser-plasma system can be used to provide full control of the polarization state of a separate "probe" laser beam; simple analytical estimates and practical considerations are provided for the design of novel photonics devices such as laser-plasma polarizers and wave plates.

  9. Propagation of light in serially coupled plasmonic nanowire dimer: Geometry dependence and polarization control

    SciTech Connect

    Singh, Danveer; Raghuwanshi, Mohit; Pavan Kumar, G. V.

    2012-09-10

    We experimentally studied plasmon-polariton-assisted light propagation in serially coupled silver nanowire (Ag-NW) dimers and probed their dependence on bending-angle between the nanowires and polarization of incident light. From the angle-dependence study, we observed that obtuse angles between the nanowires resulted in better transmission than acute angles. From the polarization studies, we inferred that light emission from junction and distal ends of Ag-NW dimers can be systematically controlled. Further, we applied this property to show light routing and polarization beam splitting in obtuse-angled Ag-NW dimer. The studied geometry can be an excellent test-bed for plasmonic circuitry.

  10. An optically controlled microwave phase stabilizer based on polarization interference technique using semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Chen, Han; Sun, Mingming; Sun, Xiaohan

    2014-03-01

    We introduce an optically controlled microwave phase stabilizer based on polarization interference technique using single semiconductor optical amplifier (SOA). A prototype with a frequency of 10 GHz is experimentally demonstrated. It provides a stable phase drift that can be linearly compensated over 10 km single-mode fiber by controlling the SOA injection current.

  11. Control of Fibrinogen Assembly by Changing a Polarity of Surfaces

    NASA Astrophysics Data System (ADS)

    Koo, Jaseung; Liu, Ying; Snow, Sara; Rambhia, Pooja; Koga, Tadanori; Rafailovich, Miriam; Galanakis, Dennis

    2009-03-01

    Thrombogenesis causes various problems associated with an interruption in the blood flow (e.g., myocardial and cerebral infarction), and a hindrance to use of blood-contact vascular biomaterials (e.g., hemodialysis and cardiopulmonary bypass) with long-term patency since undesired adsorption of blood components occurs on vessels or biomaterials, such as surface-induced thrombosis. we showed that this clotting procedure can be occurred on hydrophobic polymeric surfaces without thrombin cleavage. However, the fibrinogen fibers were not formed on the polar surface such as spun-cast polymer film with pyridine and phenol groups. We also found that ?C domains play an important role in initiation of polymerization on surface. Therefore, molecular association was inhibited on the polar surfaces due to confinement of ?C chains on the surfaces. These findings were directly applied to stent surface modification. The commercial stent consist of Co-Cr alloy forms undesired fiber formation. However, PS-r-PVPh (13% phenol) coated stent surfaces completely prevent fiber formation.

  12. 960-km SSMF transmission of 105.7-Gb/s PDM 3-PAM using directly modulated VCSELs and coherent detection.

    PubMed

    Xie, Chongjin; Dong, Po; Winzer, Peter; Gréus, C; Ortsiefer, M; Neumeyr, C; Spiga, Silvia; Müller, Michael; Amann, M-C

    2013-05-01

    We generate a 105.7-Gb/s signal by directly modulating a 1.5-µm VCSEL with a 33.35-Gbaud 3-level signal and polarization multiplexing. By using digital coherent detection, we successfully transmit the 105.7-Gb/s line rate (88.10 Gb/s net bit rate) signal over 960-km standard single-mode-fiber (SSMF) at a 20% hard-decision forward-error correction (FEC) threshold, which is at bit-error ratio (BER) of 1.5 x 10(-2) PMID:23670015

  13. Final report on LDRD project : narrow-linewidth VCSELs for atomic microsystems.

    SciTech Connect

    Chow, Weng Wah; Geib, Kent Martin; Peake, Gregory Merwin; Serkland, Darwin Keith

    2011-09-01

    Vertical-cavity surface-emitting lasers (VCSELs) are well suited for emerging photonic microsystems due to their low power consumption, ease of integration with other optical components, and single frequency operation. However, the typical VCSEL linewidth of 100 MHz is approximately ten times wider than the natural linewidth of atoms used in atomic beam clocks and trapped atom research, which degrades or completely destroys performance in those systems. This report documents our efforts to reduce VCSEL linewidths below 10 MHz to meet the needs of advanced sub-Doppler atomic microsystems, such as cold-atom traps. We have investigated two complementary approaches to reduce VCSEL linewidth: (A) increasing the laser-cavity quality factor, and (B) decreasing the linewidth enhancement factor (alpha) of the optical gain medium. We have developed two new VCSEL devices that achieved increased cavity quality factors: (1) all-semiconductor extended-cavity VCSELs, and (2) micro-external-cavity surface-emitting lasers (MECSELs). These new VCSEL devices have demonstrated linewidths below 10 MHz, and linewidths below 1 MHz seem feasible with further optimization.

  14. Final report on LDRD project :leaky-mode VCSELs for photonic logic circuits.

    SciTech Connect

    Hargett, Terry W.; Hadley, G. Ronald; Serkland, Darwin Keith; Blansett, Ethan L.; Geib, Kent Martin; Sullivan, Charles Thomas; Keeler, Gordon Arthur; Bauer, Thomas; Ongstand, Andrea; Medrano, Melissa R.; Peake, Gregory Merwin; Montano, Victoria A.

    2005-11-01

    This report describes the research accomplishments achieved under the LDRD Project ''Leaky-mode VCSELs for photonic logic circuits''. Leaky-mode vertical-cavity surface-emitting lasers (VCSELs) offer new possibilities for integration of microcavity lasers to create optical microsystems. A leaky-mode VCSEL output-couples light laterally, in the plane of the semiconductor wafer, which allows the light to interact with adjacent lasers, modulators, and detectors on the same wafer. The fabrication of leaky-mode VCSELs based on effective index modification was proposed and demonstrated at Sandia in 1999 but was not adequately developed for use in applications. The aim of this LDRD has been to advance the design and fabrication of leaky-mode VCSELs to the point where initial applications can be attempted. In the first and second years of this LDRD we concentrated on overcoming previous difficulties in the epitaxial growth and fabrication of these advanced VCSELs. In the third year, we focused on applications of leaky-mode VCSELs, such as all-optical processing circuits based on gain quenching.

  15. Transverse Mode Dynamics of VCSELs Undergoing Current Modulation

    NASA Technical Reports Server (NTRS)

    Goorjian, Peter M.; Ning, C. Z.; Agrawal, Govind

    2000-01-01

    Transverse mode dynamics of a 20-micron-diameter vertical-cavity surface-emitting laser (VCSEL) undergoing gain switching by deep current modulation is studied numerically. The direct current (dc) level is set slightly below threshold and is modulated by a large alternating current (ac). The resulting optical pulse train and transverse-mode patterns are obtained numerically. The ac frequency is varied from 2.5 GHz to 10 GHz, and the ac amplitude is varied from one-half to four times that of the dc level. At high modulation frequencies, a regular pulse train is not generated unless the ac amplitude is large enough. At all modulation frequencies, the transverse spatial profile switches from single-mode to multiple-mode pattern as the ac pumping level is increased. Optical pulse widths vary in the range 5-30 ps. with the pulse width decreasing when either the frequency is increased or the ac amplitude is decreased. The numerical modeling uses an approximation form of the semiconductor Maxwell-Bloch equations. Temporal evolution of the spatial profiles of the laser (and of carrier density) is determined without any assumptions about the type or number of modes. Keywords: VCSELs, current modulation, gain switching, transverse mode dynamics, computational modeling

  16. 1060nm VCSEL for inter-chip optical interconnection

    NASA Astrophysics Data System (ADS)

    Takaki, Keishi; Imai, Suguru; Kamiya, Shinichi; Shimizu, Hitoshi; Kawakita, Yasumasa; Hiraiwa, Koji; Takagi, Tomohiro; Shimizu, Hiroshi; Yoshida, Junji; Ishikawa, Takuya; Tsukiji, Naoki; Kasukawa, Akihiko

    2011-03-01

    The demand for the on board intra-chip optical interconnection as the "Green interconnect" have been growing so rapidly in order to catch up the speed of the performance development of high performance computing systems. In this report, our continuous study results expanding to intra-chip application in terms with power consumption and reliability are shown for the "Green" 1060nm VCSEL arrays developed by Furukawa Electric1. As the basic performance level, the clear eye opening up to 20Gbps was achieved with low power dissipation level of 160fJ/bit with voltage swing level of 130mVpp. This value would be considered as the same level of the 140fJ/bit in 10Gbps operation with 75mVpp. In the reliability test, our large scale FIT rate test had been reached up to 7.8E7 device hours and the estimated FIT rate of 30FIT/ch was obtained from no failure sample and confidence level of 90%. Our wear-out study was performed with high stress test of 170°C ambient temperature and estimated failure rate for 10years service time was 0.3FIT/ch for this mode. Our 1060nm VCSEL with low power consumption level of 140fJ/bit and high reliability of 30FIT/ch would be projected to a light source for intra-chip application.

  17. Integration of LEDs and VCSELs using fluidic self-assembly

    NASA Astrophysics Data System (ADS)

    Talghader, Joseph J.

    1998-04-01

    In this paper the integration of LEDs and VCSELs with silicon electronics using fluidic self-assembly (FSA) is reviewed. FSA is a micromechanical technique in which devices fabricated in one substrate can be integrated with systems on a target substrate. The devices to be integrated are etched into shapes or 'blocks' that match receptor sites or 'holes' in the target substrate. After etching, the blocks are suspended in a slurry. This slurry is placed in a recirculation pump along with the target substrate. The pump moves the slurry over the target substrate where the blocks fall into the holes or are swept off the substrate to be circulated again. FSA has been demonstrated with yields > 99 percent for devices of 30 micrometers and larger. Smaller devices have yet to be tested. A five mask process has been developed that successfully integrates GaAs/AlGaAs LEDs and VCSELs on silicon. The critical steps are: 1) etching the receptor sites in the silicon, 2) isolating the sites from the remainder of the substrate, and 3) bonding/contacting the blocks after assembly. The latter bonding step involves thin film metal multilayers on the block and in the receptor that form a hard solder after a low temperature bake step. The remaining steps of planarizing and interconnecting the devices are similar to those used for VLSI.

  18. Heterogeneously-integrated VCSEL using high-contrast grating on silicon

    NASA Astrophysics Data System (ADS)

    Ferrara, James; Zhu, Li; Yang, Weijian; Qiao, Pengfei; Chang-Hasnain, Connie J.

    2015-02-01

    We present a unique heterogeneous integration approach for VCSELs on silicon using eutectic bonding. An electrically pumped III-V - silicon heterogeneous VCSEL is demonstrated using a high-contrast grating (HCG) reflector on silicon. CW output power >1.5 mW, thermal resistance of 1.46 K/mW, and 5 Gb/s direct modulation is demonstrated. We also explore the possibility of an all-HCG VCSEL structure that would benefit from stronger thermal performance, larger tuning efficiency, and higher direct modulation speeds.

  19. VCSEL modeling with self-consistent models: From simple approximations to comprehensive numerical analysis

    NASA Astrophysics Data System (ADS)

    Dems, Maciej; Beling, Piotr; Gebski, Marcin; Piskorski, ?ukasz; Walczak, Jaros?aw; Kuc, Maciej; Frasunkiewicz, Leszek; Wasiak, Micha?; Sarza?a, Robert; Czyszanowski, Tomasz

    2015-03-01

    In the talk we show the process of modeling complete physical properties of VCSELs and we present a step-by-step development of its complete multi-physics model, gradually improving its accuracy. Then we introduce high contrast gratings to the VCSEL design, which strongly complicates its optical modeling, making the comprehensive multi-physics VCSEL simulation a challenging task. We show, however, that a proper choice of a self-consistent simulation algorithm can still make such a simulation a feasible one, which is necessary for an efficient optimization of the laser prior to its costly manufacturing.

  20. Real-time feedback control of millimeter-wave polarization for LHD

    SciTech Connect

    Felici, F.; Goodman, T.; Sauter, O.; Shimozuma, T.; Ito, S.; Mizuno, Y.; Kubo, S.; Mutoh, T.

    2009-01-15

    Electron cyclotron heating (ECH) is widely used in magnetic fusion devices, and the polarization of the injected millimeter-wave beams plays a crucial role in the propagation and absorption of the beam energy by the plasma. This polarization can be adjusted by grating mirror polarizers placed in the transmission lines which carry the microwaves from the power source to the plasma. In long-pulse devices such as the Large Helical Device (LHD) and ITER, it is desirable to track changes in the plasma and adjust the polarization of the ECH in real time such as to keep the absorption as high as possible and avoid shine-through which may lead to overheating of vessel components. For this purpose a real-time feedback control scheme is envisioned in which a measure of the absorption efficiency can be used to adjust the orientation of the polarizing mirrors toward an optimum. Such a setup has been tested in a low-power test stand as preparation for future implementation in the LHD ECH system. It is shown that a simple search algorithm is efficient and can in principle be used to control either the absorption efficiency or the linear polarization angle.

  1. Polarization Control in Three-Dimensional Resonant Coherent Excitation

    SciTech Connect

    Nakano, Y.; Azuma, T.; Kondo, C.; Hatakeyama, A.; Nakai, Y.; Komaki, K.; Yamazaki, Y.; Takada, E.; Murakami, T.

    2009-02-27

    We present an experimental demonstration of an ingenious technique to control the alignment of the atomic internal state in the x-ray region using a periodic crystal field. The alignment directions of Ar{sup 16+} and Fe{sup 24+} ions were readily controlled by selecting the array of atomic planes using three-dimensional resonant coherent excitation, and were probed via the anisotropy of the deexcitation x-ray emission. We applied this method to a double resonance experiment, and succeeded in controlling the population of the specific magnetic substate in a {lambda}-type three-level configuration.

  2. Dual-channel near-field control by polarizations using isotropic and inhomogeneous metasurface

    PubMed Central

    Wan, Xiang; Cai, Ben Geng; Li, Yun Bo; Cui, Tie Jun

    2015-01-01

    We propose a method for dual-channel near-field manipulations by designing isotropic but inhomogeneous metasurfaces. As example, we present a dual-channel near-field focusing metasurface device. When the device is driven by surface waves from different channels on the metasurface, the near fields will be focused at the same spatial point with different polarizations. Conversely, if a linearly polarized source is radiated at the spatial focal point, different channels will be evoked on the metasurface controlled by polarization. We fabricated and measured the metasurface device in the microwave frequency. Well agreements between the simulation and measurement results are observed. The proposed method exhibits great flexibility in controlling the surface waves and spatial waves simultaneously. It is expected that the proposed method and dual-channel device will facilitate the manipulation of near electromagnetic or optical waves in different frequency regimes. PMID:26527420

  3. Design of broadband transmission quarter-wave plates for polarization control of isolated attosecond pulses

    NASA Astrophysics Data System (ADS)

    Chen, Shujing; Lin, Chengyou; Gao, Hua

    2015-07-01

    Using a standard Levenberg-Marquardt algorithm, broadband quarter-wave plates (QWPs) with bandwidth from 3 to 18 eV in the extreme ultraviolet (EUV) region were designed using aperiodic Mo/Si multilayers. By analyzing the design results of the Mo/Si multiayers with different bilayer numbers, we found that a Mo/Si multilayer with more bilayers can achieve broader phase control, but suffers from lower total throughput and a degree of circular polarization. In addition, the pulse broadenings caused by the group delay dispersions of the designed broadband QWPs were studied, and their layer distributions were investigated. The oscillating distribution of bilayer thickness in optimized multilayers was observed, which is considered to be the reason for forming the broadband phase control. Such broadband QWPs can be applied to generate a circularly polarized broadband EUV source, such as isolated attosecond pulse, directly from a linearly polarized source.

  4. Dual-channel near-field control by polarizations using isotropic and inhomogeneous metasurface

    NASA Astrophysics Data System (ADS)

    Wan, Xiang; Cai, Ben Geng; Li, Yun Bo; Cui, Tie Jun

    2015-11-01

    We propose a method for dual-channel near-field manipulations by designing isotropic but inhomogeneous metasurfaces. As example, we present a dual-channel near-field focusing metasurface device. When the device is driven by surface waves from different channels on the metasurface, the near fields will be focused at the same spatial point with different polarizations. Conversely, if a linearly polarized source is radiated at the spatial focal point, different channels will be evoked on the metasurface controlled by polarization. We fabricated and measured the metasurface device in the microwave frequency. Well agreements between the simulation and measurement results are observed. The proposed method exhibits great flexibility in controlling the surface waves and spatial waves simultaneously. It is expected that the proposed method and dual-channel device will facilitate the manipulation of near electromagnetic or optical waves in different frequency regimes.

  5. Electric field controlled spin- and valley-polarized edge states in silicene with extrinsic Rashba effect

    NASA Astrophysics Data System (ADS)

    Yu, Zhiming; Pan, Hui; Yao, Yugui

    2015-10-01

    In the presence of extrinsic Rashba spin-orbit coupling, we find that silicene can host a quantum anomalous Hall state with spin- and valley-polarized edge states, which can be effectively controlled by the exchange field and electric field. In this state, a pair of nontrivial edge states reside in one specific valley and have a strong but opposite spin polarization. A distinctive feature of this state is that both of the spin and valley indexes of the edge states can be switched by reversing the electric field. We also present a microscopic mechanism for the origin of this state. Our findings provide an efficient way to control the topologically protected spin- and valley-polarized edge states, which is crucial for spintronics and valleytronics.

  6. Dual-channel near-field control by polarizations using isotropic and inhomogeneous metasurface.

    PubMed

    Wan, Xiang; Cai, Ben Geng; Li, Yun Bo; Cui, Tie Jun

    2015-01-01

    We propose a method for dual-channel near-field manipulations by designing isotropic but inhomogeneous metasurfaces. As example, we present a dual-channel near-field focusing metasurface device. When the device is driven by surface waves from different channels on the metasurface, the near fields will be focused at the same spatial point with different polarizations. Conversely, if a linearly polarized source is radiated at the spatial focal point, different channels will be evoked on the metasurface controlled by polarization. We fabricated and measured the metasurface device in the microwave frequency. Well agreements between the simulation and measurement results are observed. The proposed method exhibits great flexibility in controlling the surface waves and spatial waves simultaneously. It is expected that the proposed method and dual-channel device will facilitate the manipulation of near electromagnetic or optical waves in different frequency regimes. PMID:26527420

  7. Polarization-rotation resonances with subnatural widths using a control laser

    E-print Network

    Chanu, Sapam Ranjita; Bharti, Vineet; Wasan, Ajay; Natarajan, Vasant

    2013-01-01

    We demonstrate extremely narrow resonances for polarization rotation in an atomic vapor. The resonances are created using a strong control laser on the same transition, which polarizes the atoms due to optical pumping among the magnetic sublevels. As the power in the control laser is increased, successively higher-order nested polarization rotation resonances are created, with progressively narrower linewidths. We study these resonances in the $D_2$ line of Rb in a room-temperature vapor cell, and demonstrate a width of $0.14 \\, \\Gamma$ for the third-order rotation. The explanation based on a simplified $\\Lambda$V-type level structure is borne out by a density-matrix analysis of the system. The dispersive lineshape and subnatural width of the resonance lends itself naturally to applications such as laser locking to atomic transitions and precision measurements.

  8. Polarization controllable Fresnel lens using dye-doped liquid crystals

    E-print Network

    Wu, Shin-Tson

    controllable Fresnel zone plate lens is demonstrated using a photo-induced alignment of the dye-doped liquid-481 (2004). 3. S. C. Kim, S. E. Lee, and E. S. Kim, "Optical implementation of real-time incoherent 3D. Mondol, F. J. Castaño, and H. I. Smith, "Scanning-spatial-phase alignment for zone

  9. High-speed ultra-broad tuning MEMS-VCSELs for imaging and spectroscopy

    E-print Network

    Jayaraman, Vijaysekhar

    In the last 2 years, the field of micro-electro-mechanical systems tunable vertical cavity surface-emitting lasers (MEMS-VCSELs) has seen dramatic improvements in laser tuning range and tuning speed, along with expansion ...

  10. Ultrahigh speed endoscopic optical coherence tomography using micro-motor imaging catheter and VCSEL technology

    E-print Network

    Tsai, Tsung-Han

    We developed a micro-motor based miniature catheter with an outer diameter of 3mm for ultrahigh speed endoscopic optical coherence tomography (OCT) using vertical cavity surface-emitting laser (VCSEL) at a 1MHz axial scan ...

  11. 8-Gbps-per-channel radiation-tolerant VCSEL drivers for the LHC detector upgrade

    NASA Astrophysics Data System (ADS)

    Li, X.; Guo, D.; Chen, J.; Gong, D.; Hou, S.; Huang, D.; Huang, G.; Liang, F.; Liu, C.; Liu, T.; Sun, X.; Teng, P.-K.; Xiang, A. C.; Ye, J.; You, Y.; Zhao, X.

    2015-02-01

    We present ASIC designs of VCSEL drivers for a single VCSEL (LOCld1), two individual VCSELs (LOCld2) and a four-channel VCSEL array (LOCld4). This work is for new detector readout systems needed in the Large Hadron Collider upgrade program. All ASICs are fabricated in a commercial 0.25-? m Silicon-on-Sapphire CMOS technology. LOCld1 and LOCld2 have passed the 8-Gbps and 10-Gbps eye mask tests. Operating at 8 Gbps data rate, the measured total jitter of LOCld1 and LOCld2 is less than 30 ps, and the power comsuption is about 200 mW per channel with 6-mA bias current and 6.4-mA modulation current. The radiation tolerance of LOCld1 has been qualified with x-ray and high-energy neutron beam test.

  12. Q-plates as higher order polarization controllers for orbital angular momentum modes of fiber.

    PubMed

    Gregg, P; Mirhosseini, M; Rubano, A; Marrucci, L; Karimi, E; Boyd, R W; Ramachandran, S

    2015-04-15

    We demonstrate that a |q|=1/2 plate, in conjunction with appropriate polarization optics, can selectively and switchably excite all linear combinations of the first radial mode order |l|=1 orbital angular momentum (OAM) fiber modes. This enables full mapping of free-space polarization states onto fiber vector modes, including the radially (TM) and azimuthally polarized (TE) modes. The setup requires few optical components and can yield mode purities as high as ?30??dB. Additionally, just as a conventional fiber polarization controller creates arbitrary elliptical polarization states to counteract fiber birefringence and yield desired polarizations at the output of a single-mode fiber, q-plates disentangle degenerate state mixing effects between fiber OAM states to yield pure states, even after long-length fiber propagation. We thus demonstrate the ability to switch dynamically, potentially at ?GHz rates, between OAM modes, or create desired linear combinations of them. We envision applications in fiber-based lasers employing vector or OAM mode outputs, as well as communications networking schemes exploiting spatial modes for higher dimensional encoding. PMID:25872059

  13. Evolution of Developmental Control Mechanisms Long-range neural and gap junction protein-mediated cues control polarity during

    E-print Network

    Oviedo, Néstor J.

    -mediated cues control polarity during planarian regeneration Néstor J. Oviedo a,1 , Junji Morokuma a , Peter in planarians. Modulation of gap junction-dependent and neural signals specifically induces ectopic anterior of regenerative medicine. Planarians possess an accessible adult somatic stem cell population (neoblasts

  14. Polarization aberration control for hyper-NA lithographic projection optics at design stage

    NASA Astrophysics Data System (ADS)

    Liu, Xiaolin; Li, Yanqiu; Liu, Ke

    2015-08-01

    For hyper numerical aperture (NA) lithographic projection optics, not only scalar aberration but also polarization aberration (PA) should be controlled. Optical interfaces, coatings and intrinsic birefringence of lens materials can induce polarization aberration, so they cannot be ignored at design phase. There are few comprehensive and systematic studies on PA control at design phase for lithographic optics. In this paper, a lithographic projection lens with 1.2 of NA is designed, the root-mean-square of scalar aberration reach 1nm. For PA control of this system, firstly the influence of different subsets of polarization aberration on imaging performance is analyzed. The results indicate that the scalar transmission and diattenuation mainly cause critical dimension error (CDE), and the scalar phase and retardance mainly cause pattern placement error (PE). The results also show the diattenuation is the main controlled object in the process of PA control. Furthermore, a cooperative design strategy for PA control is proposed, which is to cooperate between custom coating design and the optimization of crystal orientation based on optical structure design. Through the cooperative design, the PA can be greatly reduced, especially diattenuation. The simulation results of the final system reveal that the dynamic range of CDE is suppressed from -12.7nm ~ +4.3nm to -0.1nm ~ +0.9nm after PA control, while keeping PE at an acceptable level.

  15. Color controllable polarization entanglement generation in optical fiber at telecommunication wavelengths.

    PubMed

    Karmakar, Sanjit; Meyers, Ronald E

    2015-08-10

    This article proposes a polarized entangled photon source in optical fiber with low Raman noise that features the controllable generation of specific signal and idler wavelengths (colors) by varying the pump power. The novel two color source can provide needed telecom entangled photon wavelengths for applications in quantum communications, quantum computing, and quantum imaging. PMID:26367913

  16. Coherent control of pump-probe signals of helical structures by adaptive pulse polarizations

    E-print Network

    Mukamel, Shaul

    excitons in multidimensional spectroscopy.11­14 Shaping the polarization state of the electric field-Stokes Raman spectroscopy CARS .18 Multipolar- ization optimal control two-dimensional 2D and three with a sequence of laser pulses Fig. 1 , whose electric field is given by E r, = j=1 4 Aj -¯j exp ikjr - i¯ j -¯j

  17. Polarity Control in Double-Gate, Gate-All-Around Vertically Stacked Silicon Nanowire FETs

    E-print Network

    De Micheli, Giovanni

    Polarity Control in Double-Gate, Gate-All-Around Vertically Stacked Silicon Nanowire FETs M. De stacked Double Gate (DG) Silicon Nanowire (SiNW) FETs, featuring two Gate-All-Around (GAA) electrodes (Fig of nanowires, without requiring complex transfer procedures of pre-grown nanowires on a final substrate

  18. Controlled release of cytokines using silk-biomaterials for macrophage polarization.

    PubMed

    Reeves, Andrew R D; Spiller, Kara L; Freytes, Donald O; Vunjak-Novakovic, Gordana; Kaplan, David L

    2015-12-01

    Polarization of macrophages into an inflammatory (M1) or anti-inflammatory (M2) phenotype is important for clearing pathogens and wound repair, however chronic activation of either type of macrophage has been implicated in several diseases. Methods to locally control the polarization of macrophages is of great interest for biomedical implants and tissue engineering. To that end, silk protein was used to form biopolymer films that release either IFN-? or IL-4 to control the polarization of macrophages. Modulation of the solubility of the silk films through regulation of ?-sheet (crystalline) content enabled a short-term release (4-8 h) of either cytokine, with smaller amounts released out to 24 h. Altering the solubility of the films was accomplished by varying the time that the films were exposed to water vapor. The released IFN-? or IL-4 induced polarization of THP-1 derived macrophages into the M1 or M2 phenotypes, respectively. The silk biomaterials were able to release enough IFN-? or IL-4 to repolarize the macrophage from M1 to M2 and vice versa, demonstrating the well-established plasticity of macrophages. High ?-sheet content films that are not soluble and do not release the trapped cytokines were also able to polarize macrophages that adhered to the surface through degradation of the silk protein. Chemically conjugating IFN-? to silk films through disulfide bonds allowed for longer-term release to 10 days. The release of covalently attached IFN-? from the films was also able to polarize M1 macrophages in vitro. Thus, the strategy described here offers new approaches to utilizing biomaterials for directing the polarization of macrophages. PMID:26421484

  19. Fast, high-fidelity, all-optical and dynamically-controlled polarization gate using room-temperature atomic vapor

    SciTech Connect

    Li, Runbing; Zhu, Chengjie; Deng, L.; Hagley, E. W.

    2014-10-20

    We demonstrate a fast, all-optical polarization gate in a room-temperature atomic medium. Using a Polarization-Selective-Kerr-Phase-Shift (PSKPS) technique, we selectively write a ? phase shift to one circularly-polarized component of a linearly-polarized input signal field. The output signal field maintains its original strength but acquires a 90° linear polarization rotation, demonstrating fast, high-fidelity, dynamically-controlled polarization gate operation. The intensity of the polarization-switching field used in this PKSPK-based polarization gate operation is only 2?mW/cm{sup 2}, which would be equivalent to 0.5?nW of light power (??=?800?nm) confined in a typical commercial photonic hollow-core fiber. This development opens a realm of possibilities for potential future extremely low light level telecommunication and information processing systems.

  20. A Tunable Dispersion-Free Terahertz Metadevice with Pancharatnam-Berry-Phase-Enabled Modulation and Polarization Control.

    PubMed

    Cong, Longqing; Xu, Ningning; Han, Jiaguang; Zhang, Weili; Singh, Ranjan

    2015-11-01

    It is extremely challenging to control the phase of light at will in free space. Here, Pancharatnam-Berry-phase-enabled, tunable phase control of free-space light is experimentally demonstrated in an ultrathin flexible dispersion-free metadevice. This metadevice enables the broadband conversion of linearly polarized light into any desired output polarization. PMID:26421902

  1. Two-photon coherent control of atomic collisions by light with entangled polarization

    E-print Network

    M. D. Havey; D. V. Kupriyanov; I. M. Sokolov

    2015-01-21

    We describe a new method of coherent optical control of internal dynamics of atomic collisions by means of two correlated light beams having entangled polarizations. We show that if excitation of a colliding pair of atoms is by two photons having entangled polarizations, it is possible to redirect the output fragments of the collision into certain channels with a selected type of internal transition symmetry. The transition symmetry is defined in the body-fixed coordinate frame which has random and originally unknown orientation in space.

  2. Control of polarization and dipole moment in low-dimensional semiconductor nanostructures

    SciTech Connect

    Li, L. H.; Ridha, P.; Mexis, M.; Smowton, P. M.; Blood, P.; Bozkurt, M.; Koenraad, P. M.; Patriarche, G.

    2009-11-30

    We demonstrate the control of polarization and dipole moment in semiconductor nanostructures, through nanoscale engineering of shape and composition. Rodlike nanostructures, elongated along the growth direction, are obtained by molecular beam epitaxial growth. By varying the aspect ratio and compositional contrast between the rod and the surrounding matrix, we rotate the polarization of the dominant interband transition from transverse-electric to transverse-magnetic, and modify the dipole moment producing a radical change in the voltage dependence of absorption spectra. This opens the way to the optimization of quantum dot amplifiers and electro-optical modulators.

  3. Controlling enhancement and suppression of four-wave mixing via polarized light

    SciTech Connect

    Li Changbiao; Zhang Yanpeng; Nie Zhiqiang; Du Yigang; Wang Ruimin; Song Jianping; Xiao Min

    2010-03-15

    We show that the four-wave mixing (FWM) processes in a multi-Zeeman level atomic system can be enhanced and suppressed by changing the polarization of one of the pump beams. Different polarization states of the pump beams will act on different transition pathways among the multi-Zeeman levels with different transition strengths, which affect the FWM efficiencies. An additional dress field applied to the adjacent transition can cause energy level splitting and therefore control the enhancement and suppression of the FWM processes in the system. The experimental results are in good agreement with our theoretical calculations.

  4. Spontaneous cell polarization: Feedback control of Cdc42 GTPase breaks cellular symmetry.

    PubMed

    Martin, Sophie G

    2015-11-01

    Spontaneous polarization without spatial cues, or symmetry breaking, is a fundamental problem of spatial organization in biological systems. This question has been extensively studied using yeast models, which revealed the central role of the small GTPase switch Cdc42. Active Cdc42-GTP forms a coherent patch at the cell cortex, thought to result from amplification of a small initial stochastic inhomogeneity through positive feedback mechanisms, which induces cell polarization. Here, I review and discuss the mechanisms of Cdc42 activity self-amplification and dynamic turnover. A robust Cdc42 patch is formed through the combined effects of Cdc42 activity promoting its own activation and active Cdc42-GTP displaying reduced membrane detachment and lateral diffusion compared to inactive Cdc42-GDP. I argue the role of the actin cytoskeleton in symmetry breaking is not primarily to transport Cdc42 to the active site. Finally, negative feedback and competition mechanisms serve to control the number of polarization sites. PMID:26338468

  5. Spin Control of the topological surface states in 3D topological insulators using polarized light

    NASA Astrophysics Data System (ADS)

    Gura, Anna; Secor, Jeff; Begliarbekov, Milan; Zhao, Lukas; Deng, Haiming; Krusin-Elbaum, Lia

    2013-03-01

    The topological surface states of 3D topological insulators (TIs)been shown to interact non trivially with circularly polarized light. Here we report on the study of spin-polarized currents in several 2nd generation TIs, such as Sb2Te3, Be2Te3, and Bi2Se3. In particular, to probe the robustness of the helical current surface states we will contrast the polarization dependence of the photocurrent in as grown crystals and crystals with controlled disorder introduced by magnetic and non-magnetic impurities. These result in the development of a gap in the energy spectrum of surface Dirac fermions (DFs), that is DFs acquire mass. The photo-response contrast between massless and massive Dirac fermions studied under electric field gating conditions will be presented. Supported in part by NSF-DMR-1122594

  6. Composition controlled spin polarization in Co(1-x)Fe(x)S(2) alloys.

    PubMed

    Leighton, C; Manno, M; Cady, A; Freeland, J W; Wang, L; Umemoto, K; Wentzcovitch, R M; Chen, T Y; Chien, C L; Kuhns, P L; Hoch, M J R; Reyes, A P; Moulton, W G; Dahlberg, E D; Checkelsky, J; Eckert, J

    2007-08-01

    The transition metal (TM) chalcogenides of the form TMX(2) (X = S or Se) have been studied for decades due to their interesting electronic and magnetic properties such as metamagnetism and metal-insulator transitions. In particular, the Co(1-x)Fe(x)S(2) alloys were the subject of investigation in the 1970s due to general interest in itinerant ferromagnetism. In recent years (2000-present) it has been shown, both by electronic structure calculations and detailed experimental investigations, that Co(1-x)Fe(x)S(2) is a model system for the investigation of highly spin polarized ferromagnetism. The radically different electronic properties of the two endpoint compounds (CoS(2) is a narrow bandwidth ferromagnetic metal, while FeS(2) is a diamagnetic semiconductor), in a system forming a substitutional solid solution allows for composition control of the Fermi level relative to the spin split bands, and therefore composition-controlled conduction electron spin polarization. In essence, the recent work has shown that the concept of 'band engineering' can be applied to half-metallic ferromagnets and that high spin polarization can be deliberately engineered. Experiments reveal tunability in both sign and magnitude of the spin polarization at the Fermi level, with maximum values obtained to date of 85% at low temperatures. In this paper we review the properties of Co(1-x)Fe(x)S(2) alloys, with an emphasis on properties of relevance to half-metallicity. Crystal structure, electronic structure, synthesis, magnetic properties, transport properties, direct probes of the spin polarization, and measurements of the total density of states at the Fermi level are all discussed. We conclude with a discussion of the factors that influence, or even limit, the spin polarization, along with a discussion of opportunities and problems for future investigation, particularly with regard to fundamental studies of spintronic devices. PMID:21694119

  7. Composition controlled spin polarization in Co1-xFexS2 alloys

    NASA Astrophysics Data System (ADS)

    Leighton, C.; Manno, M.; Cady, A.; Freeland, J. W.; Wang, L.; Umemoto, K.; Wentzcovitch, R. M.; Chen, T. Y.; Chien, C. L.; Kuhns, P. L.; Hoch, M. J. R.; Reyes, A. P.; Moulton, W. G.; Dahlberg, E. D.; Checkelsky, J.; Eckert, J.

    2007-08-01

    The transition metal (TM) chalcogenides of the form TMX2 (X = S or Se) have been studied for decades due to their interesting electronic and magnetic properties such as metamagnetism and metal-insulator transitions. In particular, the Co1-xFexS2 alloys were the subject of investigation in the 1970s due to general interest in itinerant ferromagnetism. In recent years (2000-present) it has been shown, both by electronic structure calculations and detailed experimental investigations, that Co1-xFexS2 is a model system for the investigation of highly spin polarized ferromagnetism. The radically different electronic properties of the two endpoint compounds (CoS2 is a narrow bandwidth ferromagnetic metal, while FeS2 is a diamagnetic semiconductor), in a system forming a substitutional solid solution allows for composition control of the Fermi level relative to the spin split bands, and therefore composition-controlled conduction electron spin polarization. In essence, the recent work has shown that the concept of 'band engineering' can be applied to half-metallic ferromagnets and that high spin polarization can be deliberately engineered. Experiments reveal tunability in both sign and magnitude of the spin polarization at the Fermi level, with maximum values obtained to date of 85% at low temperatures. In this paper we review the properties of Co1-xFexS2 alloys, with an emphasis on properties of relevance to half-metallicity. Crystal structure, electronic structure, synthesis, magnetic properties, transport properties, direct probes of the spin polarization, and measurements of the total density of states at the Fermi level are all discussed. We conclude with a discussion of the factors that influence, or even limit, the spin polarization, along with a discussion of opportunities and problems for future investigation, particularly with regard to fundamental studies of spintronic devices.

  8. Second-Harmonic-Generation Microscopy Using Excitation Beam with Controlled Polarization Pattern to Determine Three-Dimensional Molecular Orientation

    NASA Astrophysics Data System (ADS)

    Yoshiki, Keisuke; Hashimoto, Mamoru; Araki, Tsutomu

    2005-08-01

    We have developed a second-harmonic-generation (SHG) microscope using an excitation beam with a controlled polarization pattern in order to detect three-dimensional molecular orientation. The electric field at the focus is controlled three-dimensionally by modifying the polarization distribution with a parallel-aligned nematic-liquid-crystal spatial-light-modulator without any mechanical moving parts. We demonstrated that the SHG signal from an Achilles tendon, sliced so that collagen fibers were aligned parallel to the optical axis, excited by a radially polarized beam was higher than those excited by linearly polarized beams. The possibility of determinating three-dimensional molecular orientation was thus shown.

  9. Polarization mode structure in long-wavelength wafer-fused vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Volet, N.; Iakovlev, V.; Sirbu, A.; Caliman, A.; Suruceanu, G.; Mereuta, A.; Kapon, E.

    2012-06-01

    Applications of long-wavelength (? > 1 ?m) vertical-cavity surface-emitting lasers (VCSELs) generally require close control over wavelength and polarization of the emitted light. In most cases, single mode and polarization stable lasing is desired. We report here on the detailed modal analysis of wafer-fused 1550-nm wavelength VCSELs incorporating an AlGaInAs/InP active region, a re-grown circular tunnel junction (TJ) and undoped AlGaAs/GaAs distributed Bragg reflectors (DBRs). We experimentally determined the diameter of the TJ that optimizes the output power and threshold current, finding a value between 7.0 ?m and 9.5 ?m depending on the temperature. Moreover, we investigated the impact of the TJ aperture diameter on the mode structure. A large batch of devices was investigated, allowing drawing conclusions on typical behavior of these devices. The measured emission spectra show that the fundamental spatial mode is split into two orthogonal polarization modes, which are spectrally separated in wavelength by ?, used as a birefringence parameter. We observed that this parameter is independent of current but depends on the particular chip, suggesting that it is caused by stress, growth inhomogeneities, or etched mesa shape. The higher order spatial modes show similar polarization doublets with a splitting also equal to ?. This suggests that the birefringence results from effects not particular to the mechanism of mode confinement. Finally, the spectral separation ?01 between the fundamental mode and the first-order transverse mode increases linearly with current, with a slope that depends only on the TJ aperture diameter. This confirms that the mode confinement is induced by the structured TJ, and possibly also by the temperature distribution induced by the current injection.

  10. Phase-controllable spin wave generation in iron garnet by linearly polarized light pulses

    SciTech Connect

    Yoshimine, Isao; Iida, Ryugo; Shimura, Tsutomu; Satoh, Takuya; Stupakiewicz, Andrzej; Maziewski, Andrzej

    2014-07-28

    A phase-controlled spin wave was non-thermally generated in bismuth-doped rare-earth iron garnet by linearly polarized light pulses. We controlled the initial phase of the spin wave continuously within a range of 180° by changing the polarization azimuth of the excitation light. The azimuth dependences of the initial phase and amplitude of the spin wave were attributed to a combination of the inverse Cotton-Mouton effect and photoinduced magnetic anisotropy. Temporally and spatially resolved spin wave propagation was observed with a CCD camera, and the waveform was in good agreement with calculations. A nonlinear effect of the spin excitation was observed for excitation fluences higher than 100 mJ/cm{sup 2}.

  11. Ferroelectric control of the spin polarization in an organic spin valve

    NASA Astrophysics Data System (ADS)

    Sun, Dali; Xu, Xiaoshan; Jiang, Lu; Lee, Ho Nyung; Guo, Hangwen; Snijders, Paul C.; Zac Ward, T.; Gai, Zheng; Zhang, X.-G.; Shen, Jian

    2012-02-01

    Recently engineering the spin propagation in organic spin valves has shown increasingly interesting properties. In this work we demonstrate novel ferroelectric control of the spin polarization in an organic spin valve. By inserting a thin ferroelectric buffer layer between a bottom La0.67Sr0.33MnO3 (LSMO) electrode and the organic Alq3 layer, a controlled spin polarization through the ferroelectric interface is achieved. The spin valve exhibits both positive and negative magnetoresistance depending on the applied bias. We conclude that this results from the energy level shift by the ferroelectric dipoles between Alq3 and LSMO (Research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy).

  12. Frequency-induced polarization bistability in vertical-cavity surface-emitting lasers with orthogonal optical injection

    SciTech Connect

    Gatare, I.; Panajotov, K.; Sciamanna, M.

    2007-02-15

    We report theoretically on a pure frequency-induced polarization bistability in a vertical-cavity surface-emitting laser (VCSEL) subject to orthogonal optical injection, i.e., the master laser light polarization is orthogonal to that of the slave VCSEL. As the frequency detuning is scanned from negative to positive values and for a fixed injected power, the VCSEL exhibits two successive and possibly bistable polarization switchings. The first switching (from the slave laser polarization to the injected light polarization) exhibits a bistable region whose width is maximum for a given value of the injected power. Such a dependency of hysteresis width on the injected power is similar to that recently found experimentally by Hong et al.[Electron. Lett. 36, 2019 (2000)]. The bistability accompanying the second switching (from the injected light polarization back to the slave laser free-running polarization) exhibits, however, significantly different features related to the occurrence of optical chaos. Interestingly, the width of the bistable region can be tuned over a large range not only by modifying the injection parameters but also by modifying the device parameters, in particular the VCSEL linewidth enhancement factor.

  13. LKB1/AMPK and PKA control ABCB11 trafficking and polarization in hepatocytes.

    PubMed

    Homolya, László; Fu, Dong; Sengupta, Prabuddha; Jarnik, Michal; Gillet, Jean-Pierre; Vitale-Cross, Lynn; Gutkind, J Silvio; Lippincott-Schwartz, Jennifer; Arias, Irwin M

    2014-01-01

    Polarization of hepatocytes is manifested by bile canalicular network formation and activation of LKB1 and AMPK, which control cellular energy metabolism. The bile acid, taurocholate, also regulates development of the canalicular network through activation of AMPK. In the present study, we used collagen sandwich hepatocyte cultures from control and liver-specific LKB1 knockout mice to examine the role of LKB1 in trafficking of ABCB11, the canalicular bile acid transporter. In polarized hepatocytes, ABCB11 traffics from Golgi to the apical plasma membrane and endogenously cycles through the rab 11a-myosin Vb recycling endosomal system. LKB1 knockout mice were jaundiced, lost weight and manifested impaired bile canalicular formation and intracellular trafficking of ABCB11, and died within three weeks. Using live cell imaging, fluorescence recovery after photobleaching (FRAP), particle tracking, and biochemistry, we found that LKB1 activity is required for microtubule-dependent trafficking of ABCB11 to the canalicular membrane. In control hepatocytes, ABCB11 trafficking was accelerated by taurocholate and cAMP; however, in LKB1 knockout hepatocytes, ABCB11 trafficking to the apical membrane was greatly reduced and restored only by cAMP, but not taurocholate. cAMP acted through a PKA-mediated pathway which did not activate AMPK. Our studies establish a regulatory role for LKB1 in ABCB11 trafficking to the canalicular membrane, hepatocyte polarization, and canalicular network formation. PMID:24643070

  14. STUDY OF THE RADIATION HARDNESS OF VCSEL AND PIN K.K. GAN, W. FERNANDO, H.P. KAGAN, R.D. KASS, A. LAW,

    E-print Network

    Gan, K. K.

    1 STUDY OF THE RADIATION HARDNESS OF VCSEL AND PIN ARRAYS K.K. GAN, W. FERNANDO, H.P. KAGAN, R. VCSEL arrays operating at 850 nm are used to transmit optical signals while PIN arrays are used at the Super LHC (SLHC). We irradiated VCSEL and GaAs PIN arrays from three vendors and silicon PIN arrays from

  15. VCSEL based transmitter module for automotive temperature range between -55° C and +125° C

    NASA Astrophysics Data System (ADS)

    Poferl, Stefan G.; Krieg, Marcel; Hocky, Oliver; Zeeb, Eberhard

    2003-04-01

    Robust, high speed optical data bus systems are increasingly required in automobiles, not only for entertainment applications within the passenger compartment but also for engine management systems and safety sensor networks. Optoelectronic components and modules intended to be used in cars have to withstand harsh environmental conditions, e.g. they have to be operational within a wide temperature range of up to - 55 °C to +1 25 °C for several thousand hours and at the same time they have to be of very low-cost. In this paper we describe a 500 MBit/s transmitter module based on a commercial available 850 nm vertical-cavity surface-emitting laser and a bias-T driving circuit. The optical output power of the module varies only by -0.5 dBm +/- 1dB in the required temperature range without active temperature control. In addition we describe a packaging solution for the VCSEL transmitters allowing the operation of the module even in an extreme engine compartment environment, where short term temperature peaks above 125 °C appear.

  16. Photonic generation of polarization-resolved wideband chaos with time-delay concealment in three-cascaded vertical-cavity surface-emitting lasers.

    PubMed

    Liu, Huijie; Li, Nianqiang; Zhao, Qingchun

    2015-05-10

    Optical chaos generated by chaotic lasers has been widely used in several important applications, such as chaos-based communications and high-speed random-number generators. However, these applications are susceptible to degradation by the presence of time-delay (TD) signature identified from the chaotic output. Here we propose to achieve the concealment of TD signature, along with the enhancement of chaos bandwidth, in three-cascaded vertical-cavity surface-emitting lasers (VCSELs). The cascaded system is composed of an external-cavity master VCSEL, a solitary intermediate VCSEL, and a solitary slave VCSEL. Through mapping the evolutions of TD signature and chaos bandwidth in the parameter space of the injection strength and frequency detuning, photonic generation of polarization-resolved wideband chaos with TD concealment is numerically demonstrated for wide regions of the injection parameters. PMID:25967492

  17. Heterogeneously integrated long-wavelength VCSEL using silicon high contrast grating on an SOI substrate.

    PubMed

    Ferrara, James; Yang, Weijian; Zhu, Li; Qiao, Pengfei; Chang-Hasnain, Connie J

    2015-02-01

    We report an electrically pumped hybrid cavity AlGaInAs-silicon long-wavelength VCSEL using a high contrast grating (HCG) reflector on a silicon-on-insulator (SOI) substrate. The VCSEL operates at silicon transparent wavelengths ~1.57 ?m with >1 mW CW power outcoupled from the semiconductor DBR, and single-mode operation up to 65 °C. The thermal resistance of our device is measured to be 1.46 K/mW. We demonstrate >2.5 GHz 3-dB direct modulation bandwidth, and show error-free transmission over 2.5 km single mode fiber under 5 Gb/s direct modulation. We show a theoretical design of SOI-HCG serving both as a VCSEL reflector as well as waveguide coupler for an in-plane SOI waveguide, facilitating integration of VCSEL with in-plane silicon photonic circuits. The novel HCG-VCSEL design, which employs scalable flip-chip eutectic bonding, may enable low cost light sources for integrated optical links. PMID:25836117

  18. Approach to control polarization and magnetic properties for multiferroics with Dzyaloshinskii-Moriya interaction

    NASA Astrophysics Data System (ADS)

    Wang, Shuling; Li, Ruixue; Fu, Hua-Hua; Ding, Linjie; Yao, Kailun

    2014-07-01

    We propose a theoretical model for one-dimensional (charge transfer magnets with Dzyaloshinskii-Moriya (DM) interaction. By using Green's function theory, we have studied the effect of DM interaction on ferroelectric and magnetic properties, where ferroelectricity is induced through symmetric mechanism. It is shown that the uniform DM interaction reduces the polarization and makes the magnetization plateau narrow down. Moreover, the transition temperature descends as the uniform DM interaction ascends, which is attributed to the decrease of the energy gap. In addition, the staggered DM interaction, which is related to intersite distance, is also discussed. It is also found that there exists a critical point, above or below which the staggered DM interaction plays different roles on the polarization, transition temperature, and magnetic behavior. As the staggered DM interaction is larger, it enhances the polarization and transition temperature and meanwhile widens the magnetization plateau, otherwise it reduces the polarization, transition temperature, and magnetization plateau. The results provide approach to control the transition temperature and physical behavior of multiferroics.

  19. Theory of topological insulator waveguides: polarization control and the enhancement of the magneto-electric effect

    E-print Network

    Crosse, J A

    2015-01-01

    Topological insulators subject to a time-symmetry-breaking perturbation are predicted to display a magneto-electric effect that causes the electric and magnetic induction fields to mix at the material's surface. This effect induces polarization rotations of between ~1-10 mrad per interface in incident plane-polarized light normal to a multilayered structure. Here we show, theoretically and numerically, that, using a waveguide geometry with a topological insulator guide layer and dielectric cladding, it is possible to achieve rotations of between ~100-1000 mrad and generate an elliptical polarization with only a three-layered structure. Both the rotation angle and ellipticity are dependent on the permittivity contrast of the guide and cladding layers and the strength of the time-symmetry-breaking perturbation. This geometry is beneficial, not only as a way to enhance the magneto-electric effect, rendering it easier to observe, but also as a method for controlling the polarization of light in the next generatio...

  20. Polarization-controllable Airy beams generated via a photoaligned director-variant liquid crystal mask.

    PubMed

    Wei, Bing-Yan; Chen, Peng; Hu, Wei; Ji, Wei; Zheng, Li-Yang; Ge, Shi-Jun; Ming, Yang; Chigrinov, Vladimir; Lu, Yan-Qing

    2015-01-01

    Researches on Airy beams have grown explosively since the first demonstration in 2007 due to the distinguishing properties of nondiffraction, transverse acceleration and self-healing. To date, a simple and compact approach for generating Airy beams in high quality and efficiency has remained challenging. Here, we propose and demonstrate a liquid crystal (LC) polarization Airy mask (PAM) featured by spatially variant LC azimuthal director. The PAM is fabricated through photoaligning LC via a polarization-sensitive alignment agent suophonic azo dye SD1. Thanks to the special design, a novel feature of polarization-controllable switch between dual Airy beams of orthogonal circular polarization is presented. The molecular-level continuity of LC director significantly improves the quality and efficiency of resultant Airy beams. Besides, the PAM can handle intense light due to the absence of absorptive electrodes. Additional merits of compact size, low cost and broad wavelength tolerance are also exhibited. This work settles a fundamental requirement for Airy beam applications of optical manipulations, biology science and even some uncharted territories. PMID:26626737

  1. Polarization-controllable Airy beams generated via a photoaligned director-variant liquid crystal mask

    PubMed Central

    Wei, Bing-Yan; Chen, Peng; Hu, Wei; Ji, Wei; Zheng, Li-Yang; Ge, Shi-Jun; Ming, Yang; Chigrinov, Vladimir; Lu, Yan-Qing

    2015-01-01

    Researches on Airy beams have grown explosively since the first demonstration in 2007 due to the distinguishing properties of nondiffraction, transverse acceleration and self-healing. To date, a simple and compact approach for generating Airy beams in high quality and efficiency has remained challenging. Here, we propose and demonstrate a liquid crystal (LC) polarization Airy mask (PAM) featured by spatially variant LC azimuthal director. The PAM is fabricated through photoaligning LC via a polarization-sensitive alignment agent suophonic azo dye SD1. Thanks to the special design, a novel feature of polarization-controllable switch between dual Airy beams of orthogonal circular polarization is presented. The molecular-level continuity of LC director significantly improves the quality and efficiency of resultant Airy beams. Besides, the PAM can handle intense light due to the absence of absorptive electrodes. Additional merits of compact size, low cost and broad wavelength tolerance are also exhibited. This work settles a fundamental requirement for Airy beam applications of optical manipulations, biology science and even some uncharted territories. PMID:26626737

  2. The actin cytoskeleton may control the polar distribution of an auxin transport protein

    NASA Technical Reports Server (NTRS)

    Muday, G. K.; Hu, S.; Brady, S. R.; Davies, E. (Principal Investigator)

    2000-01-01

    The gravitropic bending of plants has long been linked to the changes in the transport of the plant hormone auxin. To understand the mechanism by which gravity alters auxin movement, it is critical to know how polar auxin transport is initially established. In shoots, polar auxin transport is basipetal (i.e., from the shoot apex toward the base). It is driven by the basal localization of the auxin efflux carrier complex. One mechanism for localizing this efflux carrier complex to the basal membrane may be through attachment to the actin cytoskeleton. The efflux carrier protein complex is believed to consist of several polypeptides, including a regulatory subunit that binds auxin transport inhibitors, such as naphthylphthalamic acid (NPA). Several lines of experimentation have been used to determine if the NPA binding protein interacts with actin filaments. The NPA binding protein has been shown to partition with the actin cytoskeleton during detergent extraction. Agents that specifically alter the polymerization state of the actin cytoskeleton change the amount of NPA binding protein and actin recovered in these cytoskeletal pellets. Actin-affinity columns were prepared with polymers of actin purified from zucchini hypocotyl tissue. NPA binding activity was eluted in a single peak from the actin filament column. Cytochalasin D, which fragments the actin cytoskeleton, was shown to reduce polar auxin transport in zucchini hypocotyls. The interaction of the NPA binding protein with the actin cytoskeleton may localize it in one plane of the plasma membrane, and thereby control the polarity of auxin transport.

  3. Speckle characteristics of a broad-area VCSEL in the incoherent emission regime Falko Riechert a,*, Guy Verschaffelt b

    E-print Network

    Fischer, Ingo

    Speckle characteristics of a broad-area VCSEL in the incoherent emission regime Falko Riechert a the speckle contrast of a NIR broad-area VCSEL based on the spatially incoherent emission regime that can the speckle contrast by comparing it with the speckle charac- teristics in multimode emission under cw

  4. Optically controlled microwave phase shifter based on nonlinear polarization rotation in a highly nonlinear fiber.

    PubMed

    Li, Wei; Sun, Wen Hui; Wang, Wen Ting; Zhu, Ning Hua

    2014-06-01

    This Letter reports an optically controlled microwave phase shifter with an ultra-wideband working bandwidth and a full 360° phase shifting range based on nonlinear polarization rotation (NPR) in a highly nonlinear fiber (HNLF). A continuous wave probe light is modulated by a polarization modulator (PolM) that is driven by a microwave signal to be phase shifted. The optical carrier and the first-order sidebands of the probe light experience different phase shifts due to the NPR induced by the control light in the HNLF. An optical bandpass filter is used to realize single-sideband modulation of the probe light by removing one of the first-order sidebands, as well as to reject the control light. After detecting by a photodetector, the phase of the recovered microwave signal is continuously tunable by adjusting the power of the control light. The proposed approach is theoretically analyzed and experimentally verified. A full 360° tunable phase shift is realized over an ultra-wideband frequency range from 8 to 38 GHz when the power of the control light is tuned from 0 to 570 mW. PMID:24876035

  5. Precise, motion-free polarization control in Second Harmonic Generation microscopy using a liquid crystal modulator in the infinity space

    PubMed Central

    Lien, Chi-Hsiang; Tilbury, Karissa; Chen, Shean-Jen; Campagnola, Paul J.

    2013-01-01

    Second Harmonic Generation (SHG) microscopy coupled with polarization analysis has great potential for use in tissue characterization, as molecular and supramolecular structural details can be extracted. Such measurements are difficult to perform quickly and accurately. Here we present a new method that uses a liquid crystal modulator (LCM) located in the infinity space of a SHG laser scanning microscope that allows the generation of any desired linear or circular polarization state. As the device contains no moving parts, polarization can be rotated accurately and faster than by manual or motorized control. The performance in terms of polarization purity was validated using Stokes vector polarimetry, and found to have minimal residual polarization ellipticity. SHG polarization imaging characteristics were validated against well-characterized specimens having cylindrical and/or linear symmetries. The LCM has a small footprint and can be implemented easily in any standard microscope and is cost effective relative to other technologies. PMID:24156059

  6. Flip-chip assembly of VCSELs to silicon grating couplers via laser fabricated SU8 prisms.

    PubMed

    Kaur, K S; Subramanian, A Z; Cardile, P; Verplancke, R; Van Kerrebrouck, J; Spiga, S; Meyer, R; Bauwelinck, J; Baets, R; Van Steenberge, G

    2015-11-01

    This article presents the flip-chip bonding of vertical-cavity surface-emitting lasers (VCSELs) to silicon grating couplers (GCs) via SU8 prisms. The SU8 prisms are defined on top of the GCs using non-uniform laser ablation process. The prisms enable perfectly vertical coupling from the bonded VCSELs to the GCs. The VCSELs are flip-chip bonded on top of the silicon GCs employing the laser-induced forward transfer (LIFT)-assisted thermocompression technique. An excess loss of < 1 dB at 1.55 µm measured from the bonded assemblies is reported in this paper. The results of high speed transmission experiments performed on the bonded assemblies with clear eye openings up to 20 Gb/s are also presented. PMID:26561097

  7. Optical phase modulation based on directly modulated reflection-mode OIL-VCSEL.

    PubMed

    Guo, Peng; Sun, Tao; Yang, Weijian; Parekh, Devang; Zhang, Cheng; Xie, Xiaopeng; Chang-Hasnain, Connie J; Xu, Anshi; Chen, Zhangyuan

    2013-09-23

    Optical phase modulation based on directly modulated reflection-mode optically injection-locked VCSEL is investigated based on standard OIL rate equations and reflection-mode OIL model. The phase information of both static and dynamic state is simulated. The difference of static state phase information between transmission- and reflection-mode OIL is numerically analyzed. With specific OIL parameters, the output power of directly modulated OIL-VCSEL remains constant and phase deviation of 0.934? rad is obtained. Results show that a directly modulated OIL-VCSEL can function as a key component in QPSK or 8PSK transmitters. Preliminary 2.5 Gb/s PSK modulation characteristic is demonstrated experimentally. PMID:24104103

  8. Towards high-frequency operation of polarization oscillations in spin vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Lindemann, Markus; Höpfner, Henning; Gerhardt, Nils C.; Hofmann, Martin R.; Pusch, Tobias; Michalzik, Rainer

    2015-09-01

    Compared to purely charge based devices, spintronic lasers offer promising perspectives for new superior device concepts. Especially vertical-cavity surface-emitting lasers with spin-polarization (spin-VCSELs) feature ultrafast spin and polarization dynamics. Oscillations in the circular polarization degree can be generated using pulsed spin-injection. The oscillations evolve due to the carrier-spin-photon system that is coupled for the linear modes in the VCSEL's cavity via the birefringence. The polarization oscillations are independent of the conventional relaxation oscillations and have the potential to exceed frequencies of 100 GHz. The oscillations are switchable and can be the basis for ultrafast directly modulated spin-VCSELs for, e.g., communication purposes. The polarization oscillation frequency is mainly determined by the birefringence. We show a method to tune the birefringence and thus the polarization oscillation frequency by adding mechanical strain to the substrate in the vicinity of the laser. We achieved first experimental results for high-frequency operation using 850 nm oxide-confined single-mode VCSELs. The results are compared with simulations using the spin-flip-model for high birefringence values.

  9. Linearly polarized single photon antibunching from a site-controlled InGaN quantum dot

    SciTech Connect

    Jemsson, Tomas; Machhadani, Houssaine; Karlsson, K. Fredrik; Hsu, Chih-Wei; Holtz, Per-Olof

    2014-08-25

    We report on the observation of linearly polarized single photon antibunching in the excitonic emission from a site-controlled InGaN quantum dot. The measured second order coherence function exhibits a significant dip at zero time difference, corresponding to g{sub m}{sup 2}(0)=0.90 under continuous laser excitation. This relatively high value of g{sub m}{sup 2}(0) is well understood by a model as the combination of short exciton life time (320 ps), limited experimental timing resolution and the presence of an uncorrelated broadband background emission from the sample. Our result provides the first rigorous evidence of InGaN quantum dot formation on hexagonal GaN pyramids, and it highlights a great potential in these dots as fast polarized single photon emitters if the background emission can be eliminated.

  10. Tissue-Specific Signals Control Reversible Program of Localization and Functional Polarization of Macrophages

    PubMed Central

    Okabe, Yasutaka; Medzhitov, Ruslan

    2014-01-01

    SUMMARY Tissue-resident macrophages are highly heterogeneous in terms of their functions and phenotypes as a consequence of adaptation to different tissue environments. Local tissue-derived signals are thought to control functional polarization of resident macrophages; however, the identity of these signals remains largely unknown. It is also unknown whether functional heterogeneity is a result of irreversible lineage-specific differentiation or a consequence of continuous but reversible induction of diverse functional programs. Here, we identified retinoic acid as a signal that induces tissue-specific localization and functional polarization of peritoneal macrophages through the reversible induction of transcription factor GATA6. We further found that GATA6 in macrophages regulates gut IgA production through peritoneal B-1 cells. These results provide insight into the regulation of tissue-resident macrophage functional specialization by tissue-derived signals. PMID:24792964

  11. Long-range neural and gap junction protein-mediated cues control polarity during planarian regeneration.

    PubMed

    Oviedo, Néstor J; Morokuma, Junji; Walentek, Peter; Kema, Ido P; Gu, Man Bock; Ahn, Joo-Myung; Hwang, Jung Shan; Gojobori, Takashi; Levin, Michael

    2010-03-01

    Having the ability to coordinate the behavior of stem cells to induce regeneration of specific large-scale structures would have far-reaching consequences in the treatment of degenerative diseases, acute injury, and aging. Thus, identifying and learning to manipulate the sequential steps that determine the fate of new tissue within the overall morphogenetic program of the organism is fundamental. We identified novel early signals, mediated by the central nervous system and 3 innexin proteins, which determine the fate and axial polarity of regenerated tissue in planarians. Modulation of gap junction-dependent and neural signals specifically induces ectopic anterior regeneration blastemas in posterior and lateral wounds. These ectopic anterior blastemas differentiate new brains that establish permanent primary axes re-established during subsequent rounds of unperturbed regeneration. These data reveal powerful novel controls of pattern formation and suggest a constructive model linking nervous inputs and polarity determination in early stages of regeneration. PMID:20026026

  12. Dynamic control of spin wave spectra using spin-polarized currents

    SciTech Connect

    Wang, Qi; Zhang, Huaiwu Tang, Xiaoli; Bai, Feiming; Zhong, Zhiyong; Fangohr, Hans

    2014-09-15

    We describe a method of controlling the spin wave spectra dynamically in a uniform nanostripe waveguide through spin-polarized currents. A stable periodic magnetization structure is observed when the current flows vertically through the center of nanostripe waveguide. After being excited, the spin wave is transmitted at the sides of the waveguide. Numerical simulations of spin-wave transmission and dispersion curves reveal a single, pronounced band gap. Moreover, the periodic magnetization structure can be turned on and off by the spin-polarized current. The switching process from full rejection to full transmission takes place within less than 3?ns. Thus, this type magnonic waveguide can be utilized for low-dissipation spin wave based filters.

  13. Significant electrical control of amorphous oxide thin film transistors by an ultrathin Ti surface polarity modifier

    SciTech Connect

    Cho, Byungsu; Choi, Yonghyuk; Shin, Seokyoon; Jeon, Heeyoung; Seo, Hyungtak; Jeon, Hyeongtag

    2014-01-27

    We demonstrate an enhanced electrical stability through a Ti oxide (TiO{sub x}) layer on the amorphous InGaZnO (a-IGZO) back-channel; this layer acts as a surface polarity modifier. Ultrathin Ti deposited on the a-IGZO existed as a TiO{sub x} thin film, resulting in oxygen cross-binding with a-IGZO surface. The electrical properties of a-IGZO thin film transistors (TFTs) with TiO{sub x} depend on the surface polarity change and electronic band structure evolution. This result indicates that TiO{sub x} on the back-channel serves as not only a passivation layer protecting the channel from ambient molecules or process variables but also a control layer of TFT device parameters.

  14. Theoretical study of mutual control mechanism between magnetization and polarization in multiferroic materials

    NASA Astrophysics Data System (ADS)

    Liu, Yu; Zhai, Liang-Jun; Wang, Huai-Yu

    2015-03-01

    The mutual control mechanism between magnetization and polarization in multiferroic materials is studied. The system contains a ferromagnetic sublattice and a ferroelectric sublattice. To describe the magneto-electric coupling, we propose a linear coupling Hamiltonian between ferromagnetism and ferroelectricity without microscopic derivation. This coupling enables one to retrieve the hysteresis loops measured experimentally. The thermodynamic properties of the system are calculated, such as the temperature dependences of the magnetization, polarization, internal energy and free energy. The ferromagnetic and ferroelectric hysteresis loops driven by either a magnetic or an electric field are calculated, and the magnetic spin and pseudo-spin are always flipped synchronously under the external magnetic and electric field. Our theoretical results are in agreement with the experiments. Project supported by the National Basic Research Program of China (Grant No. 2012CB927402) and the National Natural Science Foundation of China (Grant Nos. 61275028 and 11074145).

  15. Noncanonical Wnt signaling pathways in C. elegans converge on POP-1/TCF and control cell polarity.

    PubMed

    Herman, Michael A; Wu, Mingfu

    2004-05-01

    In the nematode Caenorhabditis elegans, a canonical Wnt signaling pathway controls a cell migration whereas noncanonical Wnt pathways control the polarities of individual cells. Despite the differences in the identities and interactions among canonical and noncanonical Wnt pathway components, as well as the processes they regulate, almost all C. elegans Wnt pathways involve the sole Tcf homolog, POP-1. Intriguingly, POP-1 is asymmetrically distributed between the daughters of an asymmetric cell division, with the anterior sister cell usually having a higher level of nuclear POP-1 than its posterior sister. At some divisions, asymmetric distribution of POP-1 is controlled by noncanonical Wnt signaling, but at others the asymmetry is generated independently. Recent experiments suggest that despite this elaborate anterior-posterior POP-1 asymmetry, the quantity of POP-1 protein may have less to do with the subsequent determination of fate than does the quality of the POP-1 protein in the cell. In this review, we will embark on a quest to understand Quality (1), at least from the standpoint of the effect POP/Tcf quality has on the control of cell polarity in C. elegans. PMID:14977564

  16. Routing of surface plasmons in silver nanowire networks controlled by polarization and coating.

    PubMed

    Wei, Hong; Pan, Deng; Xu, Hongxing

    2015-12-01

    Controllable propagation of electromagnetic energy in plasmonic nanowaveguides is of great importance for building nanophotonic circuits. Here, we studied the routing of surface plasmons in silver nanowire structures by combining experiments and electromagnetic simulations. The superposition of different plasmon modes results in the tunable near field patterns of surface plasmons on the nanowire. Using the quantum dot fluorescence imaging technique, we experimentally demonstrate that the near field distribution on the nanowire controls the surface plasmon transmission in the nanowire networks. By controlling the polarization of the input light or by controlling the dielectric coating on the nanowire to modulate the plasmon field distribution and guarantee the strong local field intensity at the connecting junction, the surface plasmons can be efficiently routed to the connected nanowires. Depositing a thin layer of Al2O3 film onto the nanowires can reverse the polarization dependence of the output intensity at the nanowire terminals. These results are instructive for designing functional plasmonic nanowire networks and metal-nanowire-based nanophotonic devices. PMID:26514593

  17. Routing of surface plasmons in silver nanowire networks controlled by polarization and coating

    NASA Astrophysics Data System (ADS)

    Wei, Hong; Pan, Deng; Xu, Hongxing

    2015-11-01

    Controllable propagation of electromagnetic energy in plasmonic nanowaveguides is of great importance for building nanophotonic circuits. Here, we studied the routing of surface plasmons in silver nanowire structures by combining experiments and electromagnetic simulations. The superposition of different plasmon modes results in the tunable near field patterns of surface plasmons on the nanowire. Using the quantum dot fluorescence imaging technique, we experimentally demonstrate that the near field distribution on the nanowire controls the surface plasmon transmission in the nanowire networks. By controlling the polarization of the input light or by controlling the dielectric coating on the nanowire to modulate the plasmon field distribution and guarantee the strong local field intensity at the connecting junction, the surface plasmons can be efficiently routed to the connected nanowires. Depositing a thin layer of Al2O3 film onto the nanowires can reverse the polarization dependence of the output intensity at the nanowire terminals. These results are instructive for designing functional plasmonic nanowire networks and metal-nanowire-based nanophotonic devices.

  18. Vertical-cavity surface-emitting laser (VCSEL) sources for frequency domain photon migration

    NASA Astrophysics Data System (ADS)

    O'Sullivan, Thomas D.; No, Keun-Sik; Matlock, Alex; Hill, Brian; Cerussi, Albert E.; Tromberg, Bruce J.

    2015-03-01

    Frequency domain photon migration (FDPM) uses modulated laser light to measure the bulk optical properties of turbid media and is increasingly being applied for noninvasive functional medical imaging. Though semiconductor edge emitting laser diodes (EELs) have been traditionally used for this application, we show that VCSELs exhibit performance characteristics suitable for FDPM measurements of tissue optical properties. Their output power and modulation characteristics are more than sufficient for optical property recovery. In addition, their small size, high efficiency, low cost, and simple packaging make them an attractive choice as components in clinical FDPM systems. We demonstrate a unique, compact optical probe that was enabled by VCSEL technology.

  19. Electrical characterization and application of very high speed vertical cavity surface emitting lasers (VCSELs)

    SciTech Connect

    Hietala, V.M.; Lear, K.L.; Armendariz, M.G.

    1997-04-01

    Vertical Cavity Surface Emitting Lasers (VCSELs) offer many benefits over conventional edge-emitting lasers including economical microelectronic batch processing, easy extension to 2-D arrays, and of interest here, very large intrinsic bandwidths due to reduced cavity volume. Results of electrical characterization of a 19 GHz bandwidth 850 nm VCSEL are presented. Small-signal characterization and modeling of the frequency response and device impedance is presented. Large signal performance is studied using two-tone RF and high-speed digital measurements. Appropriate drive conditions for high-speed digital applications are demonstrated.

  20. High power high repetition rate VCSEL array side-pumped pulsed blue laser

    NASA Astrophysics Data System (ADS)

    van Leeuwen, Robert; Zhao, Pu; Chen, Tong; Xu, Bing; Watkins, Laurence; Seurin, Jean-Francois; Xu, Guoyang; Miglo, Alexander; Wang, Qing; Ghosh, Chuni

    2013-03-01

    High power, kW-class, 808 nm pump modules based on the vertical-cavity surface-emitting laser (VCSEL) technology were developed for side-pumping of solid-state lasers. Two 1.2 kW VCSEL pump modules were implemented in a dual side-pumped Q-switched Nd:YAG laser operating at 946 nm. The laser output was frequency doubled in a BBO crystal to produce pulsed blue light. With 125 ?s pump pulses at a 300 Hz repetition rate 6.1 W QCW 946 nm laser power was produced. The laser power was limited by thermal lensing in the Nd:YAG rod.

  1. High performance selectively oxidized VCSELs and arrays for parallel high-speed optical interconnects

    NASA Astrophysics Data System (ADS)

    Mederer, Felix; Grabherr, Martin; Eberhard, Franz; Ecker, Irene; Jäger, Roland; Joos, Jürgen; Jung, Chistian; Kicherer, Max; King, Roger; Schnitzer, Peter; Unold, Heiko; Wiedenmann, Dieter; Ebeling, Karl Joachim

    We introduce a new layout for high-bandwidth single-mode selectively oxidized vertical-cavity surface-emitting laser (VCSEL) arrays operating at 980 nm or 850 nm emission wavelength for substrate or epitaxial side emission. Coplanar feeding lines and polyimide passivation are used to reduce electrical parasitics in top-emitting GaAs and bottom-emitting InGaAs VCSELs. In order to enhance fundamental single-mode emission for larger devices of reduced series resistance a surface relief transverse mode filter is employed. Fabricated VCSELs are applied in various interconnect schemes. In detail, we demonstrate 2.5 Gb/s pseudo-random data transmission with GaAs VCSELs at an emission wavelength of ?=835 nm over 120 ?m core diameter step index plastic-optical fiber (POF) of 2.5 m length. InGaAs quantum-well based VCSELs at 935 nm emission wavelength are investigated for use in perfluorinated graded-index plastic-optical fiber (GI-POF) links. We obtain a 7 Gb/s pseudo random bit sequence (PRBS) non-return-to-zero (NRZ) data transmission over 80 m long 155 ?m diameter GI-POF. We investigate data transmission over standard 1300 nm, 9 ?m core diameter single-mode fiber using selectively oxidized single-mode GaAs or InGaAs VCSELs. We achieve biased 3 Gb/s and bias-free 1 Gb/s pseudo-random data transmission over 4.3 km at 830 nm emission wavelength where a simple fiber mode filter is used to suppress intermodal dispersion caused by the second order fiber mode. For the first time, we demonstrate 12.5 Gb/s data rate transmission of PRBS signals over 100 m graded-index multimode fiber or 1 km single-mode fiber using high performance single-mode GaAs VCSELs of 12.3 GHz modulation bandwidth emitting at ?=850 nm. Longer wave-length InGaAs VCSELs with emission at ?=1130 nm are used to transmit 2.5 Gb/s signals over 10 km of 9 ?m standard fiber. For all data transmission experiments bit-error rates (BER) remain better than 10-11 for transmission of PRBS signals for back-to-back (BTB) testing as well as for fiber transmission.

  2. Reversible control of spin-polarized supercurrents in ferromagnetic Josephson junctions.

    PubMed

    Banerjee, N; Robinson, J W A; Blamire, M G

    2014-01-01

    Magnetic inhomogeneity at a superconductor (S)-ferromagnet (F) interface converts spin-singlet Cooper pairs into spin-one triplet pairs. These pairs are immune to the pair-breaking exchange field in F and support a long-range proximity effect. Although recent experiments have confirmed the existence of spin-polarized triplet supercurrents in S-F-S Josephson junctions, reversible control of the supercurrent has been impossible because of the robust preconfigured nature of the inhomogeneity. Here, we use a barrier comprising three F layers whose relative magnetic orientation, and hence the interfacial inhomogeneity, can be controlled by small magnetic fields; we show that this enables full control of the triplet supercurrent and, by using finite element micromagnetic simulations, we can directly relate the experimental data to the theoretical models which provide a general framework to understand the role played by magnetic states in long-range supercurrent modulation. PMID:25154467

  3. Controlled Polar Asymmetry of Few-Cycle and Intense Mid-Infrared Pulses

    E-print Network

    Schmidt, Christian; Mayer, Bernhard; Pashkin, Alexej; Leitenstorfer, Alfred; Seletskiy, Denis V

    2015-01-01

    We demonstrate synthesis of super-octave-spanning and phase-locked transients in the multi-terahertz frequency range with amplitudes exceeding 13 MV/cm. Sub-cycle polar asymmetry of the electric field is adjusted by changing the relative phase between superposed fundamental and second harmonic components. The resultant broken symmetry of the field profile is directly resolved via ultrabroadband electro-optic sampling. Access to such waveforms provides a direct route for control of low-energy degrees of freedom in condensed matter as well as non-perturbative light-matter interactions.

  4. Controllable binding of polar molecules and metastability of one-dimensional gases with attractive dipole forces.

    PubMed

    Byrd, Jason N; Montgomery, John A; Côté, Robin

    2012-08-24

    We explore one-dimensional samples of ultracold polar molecules with attractive dipole-dipole interactions and show the existence of a repulsive barrier caused by a strong quadrupole interaction between molecules. This barrier can stabilize a gas of ultracold KRb molecules and even lead to long-range wells supporting bound states between the molecules. The properties of these wells can be controlled by external electric fields, allowing the formation of long polymerlike chains of KRb and studies of quantum phase transitions by varying the effective interaction between molecules. We discuss the generalization of those results to other systems. PMID:23002744

  5. Impact of optical feedback on current-induced polarization behavior of 1550 nm vertical-cavity surface-emitting lasers.

    PubMed

    Deng, Tao; Wu, Zheng-Mao; Xie, Yi-Yuan; Wu, Jia-Gui; Tang, Xi; Fan, Li; Panajotov, Krassimir; Xia, Guang-Qiong

    2013-06-01

    Polarization switching (PS) between two orthogonal linearly polarized fundamental modes is experimentally observed in commercial free-running 1550 nm vertical-cavity surface-emitting lasers (VCSELs) (Raycan). The characteristics of this PS are strongly modified after introducing a polarization-preserved (PP) or polarization-orthogonal (PO) optical feedback. Under the case that the external cavity is approximately 30 cm, the PP optical feedback results in the PS point shifting toward a lower injection current, and the region within which the two polarization modes coexist is enlarged with the increase of the PP feedback strength. Under too-strong PP feedback levels, the PS disappears. The impact of PO optical feedback on VCSEL polarization behavior is quite similar to that of PP optical feedback, but larger feedback strength is needed to obtain similar results. PMID:23736341

  6. Controlled polarity of sputter-deposited aluminum nitride on metals observed by aberration corrected scanning transmission electron microscopy

    SciTech Connect

    Harumoto, T.; Sannomiya, T.; Matsukawa, Y.; Muraishi, S.; Shi, J.; Nakamura, Y.; Sawada, H.; Tanaka, T.; Tanishiro, Y.; Takayanagi, K.

    2013-02-28

    The polarity determination process of sputter-deposited aluminum nitride (AlN) on metals has been analyzed using aberration corrected atomic resolution scanning transmission electron microscope. Direct growth of c-axis orientated AlN on face centered cubic metals (fcc) (111) with the local epitaxy has been observed, and the polarity was determined at the AlN/metal interface. We found that the AlN polarity can be controlled by the base metal layer: N-polarity AlN grows on Pt(111) while Al-polarity AlN forms on Al(111). Based on these results, the growth mechanism of AlN on metals is discussed.

  7. Transverse Mode Dynamics of VCSELs Through Space-Time Domain Simulation

    NASA Technical Reports Server (NTRS)

    Goorjian, Peter M.; Ning, Cun-Zheng; Saini, Subhash (Technical Monitor)

    1999-01-01

    Modeling and simulation are important to understand laser operation and to optimize and design device functions. Numerical simulation of VCSEL (Vertical Cavity Surface Emitting Lasers) has been largely based on solving time-independent Helmholtz equation or time dependent coupled mode equations. There are various advantages for choosing these approaches. However, the disadvantages are also apparent. The former cannot handle dynamical mode competition seen in VCSELs, while the latter assumes a given type and number of modes a priori. Furthermore, the microscopic physics of heterstructures and electron-hole plasma is very often represented by a few parameters such as linear gain coefficients and the linewidth enhancement factor. These are over simplification of space and frequency (wavelength) dependent gain and refractive index functions. When the space-time dynamical operation of VCSELs becomes important, these simple approximations become questionable. In this paper, we apply a recently developed model for edge-emitting lasers to a gain guided VCSEL for space-time domain simulation. This model takes into account the actual nonlinear dependence of gain and refractive index on frequency and carrier density within the frame work of the effective Bloch equations. The corresponding partial differential equations are solved directly by finite difference methods. Laser behavior with increasing pumping current is investigated in detail. Special attention is paid to the dynamical competition of the transverse modes.

  8. Optical injection locking of transverse modes in 1.3-µm wavelength coupled-VCSEL arrays.

    PubMed

    Long, C M; Mutter, L; Dwir, B; Mereuta, A; Caliman, A; Sirbu, A; Iakovlev, V; Kapon, E

    2014-09-01

    Optical injection locking of 1.3-µm phase-locked VCSEL arrays defined by patterned tunnel junctions and wafer fusion is investigated experimentally and theoretically. The impact of the overlap between the master laser injection beam and the injected modes is demonstrated and explained with a rate equation model that incorporates the spatial variations. PMID:25321494

  9. Spasers, VCSELs, and Surface plasmon emitting diodes (SPED): their unique features and figures of merit

    E-print Network

    Khurgin, Jacob B

    2013-01-01

    We compare fundamental characteristics of proposed electrically pumped subwavelength plasmonic lasers (spasers) with ubiquitous all-dielectric semiconductor micro-lasers (VCSEL) and indicate their close similarities as well as large differences in performance (threshold, efficiency, coherence and speed). These results should assist researchers in making informed choice of the emitter for each particular opto-electronic application.

  10. IEEE PHOTONICS TECHNOLOGY LETTERS. VOL. 7, NO. 5. MAY 1995 Coherence of VCSEL's for

    E-print Network

    Rocca, Jorge J.

    -modecoherence to 16 mm for 5 ns pulses. For holograms smaller than 0.6 mm in size the density of information that can is increasing interest in free-space global Tholographic interconnects for optical computers [11, [2] and two- generated hologram arrays to route the beams [3]. VCSEL's appear well suited to this application since

  11. Fiber Fabry-Perot interferometer (FFPI) sensor using vertical cavity surface emitting laser (VCSEL

    E-print Network

    Lee, Kyung-Woo

    2006-10-30

    for square, triangular, saw-tooth waveforms at frequencies from 10kHz to 100kHz. The dependence of VCSEL frequency on the dc bias current was determined from spectral measurements to be ~165GHz/mA. An independent measurement of this quantity based on counting...

  12. The oxide defined VCSEL-based smart pixels for the optical database filter

    SciTech Connect

    Pu, R.; Hayes, E.; Jurrat, R.; Stanko, P.J.; Wilmsen, C.W.; Choquette, K.; Geib, K.; Hou, H.Q.

    1997-04-01

    This paper presents the construction of the smart pixel arrays which perform AND and XOR functions with three-input and one-output optical signals for the application of an optical database filter. The device is based on oxide confined VCSELs bump bonded to GaAs MESFET pixels. The MSM photodetectors are monolithically integrated with MESFETs.

  13. VCSEL Laser System for Atomic Clocks Nathan Belcher REU program, College of William and Mary

    E-print Network

    Novikova, Irina

    VCSEL Laser System for Atomic Clocks Nathan Belcher REU program, College of William and Mary I of my project is to create a prototype atomic clock, and this summer's research has been all about modulation with rf signals, and use in miniature atomic clocks. This paper will describe the theory behind

  14. Dynamic nuclear polarization and optimal control spatial-selective 13C MRI and MRS

    NASA Astrophysics Data System (ADS)

    Vinding, Mads S.; Laustsen, Christoffer; Maximov, Ivan I.; Søgaard, Lise Vejby; Ardenkjær-Larsen, Jan H.; Nielsen, Niels Chr.

    2013-02-01

    Aimed at 13C metabolic magnetic resonance imaging (MRI) and spectroscopy (MRS) applications, we demonstrate that dynamic nuclear polarization (DNP) may be combined with optimal control 2D spatial selection to simultaneously obtain high sensitivity and well-defined spatial restriction. This is achieved through the development of spatial-selective single-shot spiral-readout MRI and MRS experiments combined with dynamic nuclear polarization hyperpolarized [1-13C]pyruvate on a 4.7 T pre-clinical MR scanner. The method stands out from related techniques by facilitating anatomic shaped region-of-interest (ROI) single metabolite signals available for higher image resolution or single-peak spectra. The 2D spatial-selective rf pulses were designed using a novel Krotov-based optimal control approach capable of iteratively fast providing successful pulse sequences in the absence of qualified initial guesses. The technique may be important for early detection of abnormal metabolism, monitoring disease progression, and drug research.

  15. Radial polar histogram: obstacle avoidance and path planning for robotic cognition and motion control

    NASA Astrophysics Data System (ADS)

    Wang, Po-Jen; Keyawa, Nicholas R.; Euler, Craig

    2012-01-01

    In order to achieve highly accurate motion control and path planning for a mobile robot, an obstacle avoidance algorithm that provided a desired instantaneous turning radius and velocity was generated. This type of obstacle avoidance algorithm, which has been implemented in California State University Northridge's Intelligent Ground Vehicle (IGV), is known as Radial Polar Histogram (RPH). The RPH algorithm utilizes raw data in the form of a polar histogram that is read from a Laser Range Finder (LRF) and a camera. A desired open block is determined from the raw data utilizing a navigational heading and an elliptical approximation. The left and right most radii are determined from the calculated edges of the open block and provide the range of possible radial paths the IGV can travel through. In addition, the calculated obstacle edge positions allow the IGV to recognize complex obstacle arrangements and to slow down accordingly. A radial path optimization function calculates the best radial path between the left and right most radii and is sent to motion control for speed determination. Overall, the RPH algorithm allows the IGV to autonomously travel at average speeds of 3mph while avoiding all obstacles, with a processing time of approximately 10ms.

  16. Topological control of the Caulobacter cell cycle circuitry by a polarized single-domain PAS protein

    PubMed Central

    Sanselicio, Stefano; Bergé, Matthieu; Théraulaz, Laurence; Radhakrishnan, Sunish Kumar; Viollier, Patrick H.

    2015-01-01

    Despite the myriad of different sensory domains encoded in bacteria, only a few types are known to control the cell cycle. Here we use a forward genetic screen for Caulobacter crescentus motility mutants to identify a conserved single-domain PAS (Per-Arnt-Sim) protein (MopJ) with pleiotropic regulatory functions. MopJ promotes re-accumulation of the master cell cycle regulator CtrA after its proteolytic destruction is triggered by the DivJ kinase at the G1-S transition. MopJ and CtrA syntheses are coordinately induced in S-phase, followed by the sequestration of MopJ to cell poles in Caulobacter. Polarization requires Caulobacter DivJ and the PopZ polar organizer. MopJ interacts with DivJ and influences the localization and activity of downstream cell cycle effectors. Because MopJ abundance is upregulated in stationary phase and by the alarmone (p)ppGpp, conserved systemic signals acting on the cell cycle and growth phase control are genetically integrated through this conserved single PAS-domain protein. PMID:25952018

  17. Optical control of hard X-ray polarization by electron injection in a laser wakefield accelerator

    NASA Astrophysics Data System (ADS)

    Schnell, Michael; Sävert, Alexander; Uschmann, Ingo; Reuter, Maria; Nicolai, Maria; Kämpfer, Tino; Landgraf, Björn; Jäckel, Oliver; Jansen, Oliver; Pukhov, Alexander; Kaluza, Malte Christoph; Spielmann, Christian

    2013-09-01

    Laser-plasma particle accelerators could provide more compact sources of high-energy radiation than conventional accelerators. Moreover, because they deliver radiation in femtosecond pulses, they could improve the time resolution of X-ray absorption techniques. Here we show that we can measure and control the polarization of ultra-short, broad-band keV photon pulses emitted from a laser-plasma-based betatron source. The electron trajectories and hence the polarization of the emitted X-rays are experimentally controlled by the pulse-front tilt of the driving laser pulses. Particle-in-cell simulations show that an asymmetric plasma wave can be driven by a tilted pulse front and a non-symmetric intensity distribution of the focal spot. Both lead to a notable off-axis electron injection followed by collective electron-betatron oscillations. We expect that our method for an all-optical steering is not only useful for plasma-based X-ray sources but also has significance for future laser-based particle accelerators.

  18. Optical control of hard X-ray polarization by electron injection in a laser wakefield accelerator

    PubMed Central

    Schnell, Michael; Sävert, Alexander; Uschmann, Ingo; Reuter, Maria; Nicolai, Maria; Kämpfer, Tino; Landgraf, Björn; Jäckel, Oliver; Jansen, Oliver; Pukhov, Alexander; Kaluza, Malte Christoph; Spielmann, Christian

    2013-01-01

    Laser-plasma particle accelerators could provide more compact sources of high-energy radiation than conventional accelerators. Moreover, because they deliver radiation in femtosecond pulses, they could improve the time resolution of X-ray absorption techniques. Here we show that we can measure and control the polarization of ultra-short, broad-band keV photon pulses emitted from a laser-plasma-based betatron source. The electron trajectories and hence the polarization of the emitted X-rays are experimentally controlled by the pulse-front tilt of the driving laser pulses. Particle-in-cell simulations show that an asymmetric plasma wave can be driven by a tilted pulse front and a non-symmetric intensity distribution of the focal spot. Both lead to a notable off-axis electron injection followed by collective electron–betatron oscillations. We expect that our method for an all-optical steering is not only useful for plasma-based X-ray sources but also has significance for future laser-based particle accelerators. PMID:24026068

  19. Enhancing the modulation bandwidth of VCSELs to the millimeter-waveband using strong transverse slow-light feedback.

    PubMed

    Ahmed, Moustafa; Bakry, Ahmed; Alghamdi, Mohamed S; Dalir, Hamed; Koyama, Fumio

    2015-06-15

    We present modeling on the millimeter (mm)-wave modulation of vertical-cavity surface-emitting laser (VCSEL) with a transverse coupled cavity (TCC). We show that strong slow-light feedback can induce 300% boosting of the modulation bandwidth of the TCC-VCSEL. Also, the strong lateral feedback can induce resonance modulation over passbands centered on frequencies as high as 3.8 times the VCSEL bandwidth. The slow-light feedback is modeled by a time-delay rate equation model that takes into account the multiple round trips as well as the optical loss and phase delay in each round trip in the feedback cavity. PMID:26193516

  20. In-situ OTDR for low-cost optical networks using a single-mode 850-nm VCSEL.

    SciTech Connect

    Geib, Kent Martin; Peake, Gregory Merwin; Serkland, Darwin Keith; Keeler, Gordon Arthur

    2005-04-01

    A new approach to optical time-domain reflectometry (OTDR) is proposed that will enable distributed fault monitoring in singlemode VCSEL-based networks. In situ OTDR uses the transmitter VCSEL already resident in data transceivers as both emitter and resonant-cavity photodiode for fault location measurements. Also valuable at longer wavelengths, the concept is demonstrated here using an 850 nm oxide-confined VCSEL and simple electronics. The dead times and sensitivity obtained are adequate to detect the majority of faults anticipated in local- and metropolitan-area networks.

  1. Muscle stem cell fate is controlled by the cell-polarity protein Scrib.

    PubMed

    Ono, Yusuke; Urata, Yoshishige; Goto, Shinji; Nakagawa, Shunsuke; Humbert, Patrick O; Li, Tao-Sheng; Zammit, Peter S

    2015-02-24

    Satellite cells are resident skeletal muscle stem cells that supply myonuclei for homeostasis, hypertrophy, and repair in adult muscle. Scrib is one of the major cell-polarity proteins, acting as a potent tumor suppressor in epithelial cells. Here, we show that Scrib also controls satellite-cell-fate decisions in adult mice. Scrib is undetectable in quiescent cells but becomes expressed during activation. Scrib is asymmetrically distributed in dividing daughter cells, with robust accumulation in cells committed to myogenic differentiation. Low Scrib expression is associated with the proliferative state and preventing self-renewal, whereas high Scrib levels reduce satellite cell proliferation. Satellite-cell-specific knockout of Scrib in mice causes a drastic and insurmountable defect in muscle regeneration. Thus, Scrib is a regulator of tissue stem cells, controlling population expansion and self-renewal with Scrib expression dynamics directing satellite cell fate. PMID:25704816

  2. Control of exciton spin statistics through spin polarization in organic optoelectronic devices

    PubMed Central

    Wang, Jianpu; Chepelianskii, Alexei; Gao, Feng; Greenham, Neil C.

    2012-01-01

    Spintronics based on organic semiconductor materials is attractive because of its rich fundamental physics and potential for device applications. Manipulating spins is obviously important for spintronics, and is usually achieved by using magnetic electrodes. Here we show a new approach where spin populations can be controlled primarily by energetics rather than kinetics. We find that exciton spin statistics can be substantially controlled by spin-polarizing carriers after injection using high magnetic fields and low temperatures, where the Zeeman energy is comparable with the thermal energy. By using this method, we demonstrate that singlet exciton formation can be suppressed by up to 53% in organic light-emitting diodes, and the dark conductance of organic photovoltaic devices can be increased by up to 45% due to enhanced formation of triplet charge-transfer states, leading to less recombination to the ground state. PMID:23149736

  3. LabVIEW-based control software for para-hydrogen induced polarization instrumentation.

    PubMed

    Agraz, Jose; Grunfeld, Alexander; Li, Debiao; Cunningham, Karl; Willey, Cindy; Pozos, Robert; Wagner, Shawn

    2014-04-01

    The elucidation of cell metabolic mechanisms is the modern underpinning of the diagnosis, treatment, and in some cases the prevention of disease. Para-Hydrogen induced polarization (PHIP) enhances magnetic resonance imaging (MRI) signals over 10,000 fold, allowing for the MRI of cell metabolic mechanisms. This signal enhancement is the result of hyperpolarizing endogenous substances used as contrast agents during imaging. PHIP instrumentation hyperpolarizes Carbon-13 ((13)C) based substances using a process requiring control of a number of factors: chemical reaction timing, gas flow, monitoring of a static magnetic field (Bo), radio frequency (RF) irradiation timing, reaction temperature, and gas pressures. Current PHIP instruments manually control the hyperpolarization process resulting in the lack of the precise control of factors listed above, resulting in non-reproducible results. We discuss the design and implementation of a LabVIEW based computer program that automatically and precisely controls the delivery and manipulation of gases and samples, monitoring gas pressures, environmental temperature, and RF sample irradiation. We show that the automated control over the hyperpolarization process results in the hyperpolarization of hydroxyethylpropionate. The implementation of this software provides the fast prototyping of PHIP instrumentation for the evaluation of a myriad of (13)C based endogenous contrast agents used in molecular imaging. PMID:24784636

  4. LabVIEW-based control software for para-hydrogen induced polarization instrumentation

    SciTech Connect

    Agraz, Jose Grunfeld, Alexander; Li, Debiao; BIRI, Cedars Sinai Medical Center, West Hollywood, California 90048 ; Cunningham, Karl; Willey, Cindy; Pozos, Robert; Wagner, Shawn

    2014-04-15

    The elucidation of cell metabolic mechanisms is the modern underpinning of the diagnosis, treatment, and in some cases the prevention of disease. Para-Hydrogen induced polarization (PHIP) enhances magnetic resonance imaging (MRI) signals over 10 000 fold, allowing for the MRI of cell metabolic mechanisms. This signal enhancement is the result of hyperpolarizing endogenous substances used as contrast agents during imaging. PHIP instrumentation hyperpolarizes Carbon-13 ({sup 13}C) based substances using a process requiring control of a number of factors: chemical reaction timing, gas flow, monitoring of a static magnetic field (B{sub o}), radio frequency (RF) irradiation timing, reaction temperature, and gas pressures. Current PHIP instruments manually control the hyperpolarization process resulting in the lack of the precise control of factors listed above, resulting in non-reproducible results. We discuss the design and implementation of a LabVIEW based computer program that automatically and precisely controls the delivery and manipulation of gases and samples, monitoring gas pressures, environmental temperature, and RF sample irradiation. We show that the automated control over the hyperpolarization process results in the hyperpolarization of hydroxyethylpropionate. The implementation of this software provides the fast prototyping of PHIP instrumentation for the evaluation of a myriad of {sup 13}C based endogenous contrast agents used in molecular imaging.

  5. Optically controlled polarizer using a ladder transition for high speed Stokesmetric Imaging and Quantum Zeno Effect based optical logic.

    PubMed

    Krishnamurthy, Subramanian; Wang, Y; Tu, Y; Tseng, S; Shahriar, M S

    2013-10-21

    We demonstrate an optically controlled polarizer at ~1323 nm using a ladder transition in a Rb vapor cell. The lower leg of the 5S(1/2),F = 1->5P(1/2),F = 1,2->6S(1/2),F = 1,2 transitions is excited by a Ti:Sapphire laser locked to a saturated absorption signal, representing the control beam. A tunable fiber laser at ~1323 nm is used to excite the upper leg of the transitions, representing the signal beam. When the control beam is linearly polarized, it produces an excitation of the intermediate level with a particular orientation of the angular momentum. Under ideal conditions, this orientation is transparent to the signal beam if it has the same polarization as the control beam and is absorbed when it is polarized orthogonally. We also present numerical simulations of the system using a comprehensive model which incorporates all the relevant Zeeman sub-levels in the system, and identify means to improve the performance of the polarizer. A novel algorithm to compute the evolution of large scale quantum system enabled us to perform this computation, which may have been considered too cumbersome to carry out previously. We describe how such a polarizer may serve as a key component for high-speed Stokesmetric imaging. We also show how such a polarizer, combined with an optically controlled waveplate, recently demonstrated by us, can be used to realize a high speed optical logic gate by making use of the Quantum Zeno Effect. Finally, we describe how such a logic gate can be realized at an ultra-low power level using a tapered nanofiber embedded in a vapor cell. PMID:24150297

  6. Fiber optic polarization synthesizer

    NASA Astrophysics Data System (ADS)

    Scholl, Bernhard; Rasmussen, Jens C.; Schmitt, Hans J.

    1996-08-01

    Rotatable fiber loops are commonly used to change the state of polarization in fiber optic transmission systems. As an improvement of such a system we describe a feedback controlled polarization transformer which operates at its output prot as a polarization synthesizer. The whole setup allows a very efficient polarization adjustment with a stable and well known state of polarization.

  7. Electrically controlled spin polarization and selection in a topological insulator sandwiched between ferromagnetic electrodes

    SciTech Connect

    Guo, Junji; Liao, Wenhu Zhao, Heping; Zhou, Guanghui

    2014-01-14

    We theoretically investigate the electrically controllable spin polarization and selective efficiency of the edge state Dirac electron in a two-dimensional topological insulator (TI) sandwiched between ferromagnetic (FM) electrodes by using the method of Keldysh nonequilibrium Green's function. A nearly full spin polarization of the topological edge state with giant inversion of ?80% is observed, which is much higher than the value previously reported. Moreover, the selective efficiency for spin-up electrons under the modulation of the parallel configuration of FM electrodes has been demonstrated to be larger than 95% for the first time, while that for spin-down electrons in the antiparallel case is higher than 90% in a wide energy range, owing to the inter-edge spin tunneling induced backscattering and spin dephasing effect. The obtained results may provide a deeper understanding of the TI edge states and a valuable guidance to design spin switch and filter with high on-off speed and selective efficiency based on TIs.

  8. Polarization control in high power microwaves from a rectangular cross section gyrotron

    SciTech Connect

    Hochman, J.M.; Gilgenbach, R.M.; Jaynes, R.J.; Rintamaki, J.I.; Lau, Y.Y.; Spencer, T.A.

    1997-12-31

    The authors summarize the results of experiments on a gyrotron utilizing rectangular-cross-section (RCS) interaction cavities. Current issues under investigation include polarization control as a function of magnetic field, power versus pulselength of microwave emission, and mode competition. The electron beam driver producing an annular beam is the Michigan Electron Long Beam Accelerator (MELBA). The annular e-beam is spun up into an axis-encircling beam by passing it through a magnetic cusp prior to entering the RCS interaction cavity. Initial experimental results show a high degree of polarization [P(TE{sub 10})/P(TE{sub 01}) = 30 or 1/30] as a function of cavity fields. Megawatt microwave output shifts from the fundamental mode, which dominates the next order mode by an order of magnitude, to the next order mode as the field is raised from 1.4 to 1.7 kGauss. Frequency measurements using microstrip bandpass filters and a superheterodyne mixer support this result as well as MAGIC simulations. MAGIC code simulations using various magnetic fields will be presented as well as results utilizing the E-gun code.

  9. Coherent electronic wave packet motion in C(60) controlled by the waveform and polarization of few-cycle laser fields.

    PubMed

    Li, H; Mignolet, B; Wachter, G; Skruszewicz, S; Zherebtsov, S; Süssmann, F; Kessel, A; Trushin, S A; Kling, Nora G; Kübel, M; Ahn, B; Kim, D; Ben-Itzhak, I; Cocke, C L; Fennel, T; Tiggesbäumker, J; Meiwes-Broer, K-H; Lemell, C; Burgdörfer, J; Levine, R D; Remacle, F; Kling, M F

    2015-03-27

    Strong laser fields can be used to trigger an ultrafast molecular response that involves electronic excitation and ionization dynamics. Here, we report on the experimental control of the spatial localization of the electronic excitation in the C_{60} fullerene exerted by an intense few-cycle (4 fs) pulse at 720 nm. The control is achieved by tailoring the carrier-envelope phase and the polarization of the laser pulse. We find that the maxima and minima of the photoemission-asymmetry parameter along the laser-polarization axis are synchronized with the localization of the coherent electronic wave packet at around the time of ionization. PMID:25860740

  10. DKIST controls model for synchronization of instrument cameras, polarization modulators, and mechanisms

    NASA Astrophysics Data System (ADS)

    Ferayorni, Andrew; Beard, Andrew; Berst, Chris; Goodrich, Bret

    2014-07-01

    The Daniel K. Inouye Solar Telescope (DKIST) will include facility instruments that perform polarimetric observations of the sun. In order for an instrument to successfully perform these observations its Instrument Controller (IC) software must be able to tightly synchronize the activities of its sub-systems including polarization modulators, cameras, and mechanisms. In this paper we discuss the DKIST control model for synchronizing these sub-systems without the use of hardware trigger lines by using the DKIST Time Reference And Distribution System (TRADS) as a common time base and through sub-system control interfaces that support configuring the timing and cadence of their behavior. The DKIST Polarization Modulator Controller System (PMCS) provides an interface that allows the IC to characterize the rotation of the modulator in terms of a reference time (t0), rate, and start state. The DKIST Virtual Camera (VC) provides a complimentary interface that allows data acquisitions and accumulation sequences to be specified using a reference time (t0), rate, and execution block time slices, which are cumulative offsets from t0. Re-configuration of other instrument mechanisms such as filter, slits, or steering mirrors during the observation is the responsibility of the IC and must be carefully scheduled at known and pre-determined gaps in the VC data acquisition sequence. The DKIST TRADS provides an IEEE-1588-2008 Precision Time Protocol (PTP) service that is used to synchronize the activities of instrument sub-systems. The modulator, camera, and mechanism sub-systems subscribe to this service and can therefore perform their tasks according to a common time base. In this paper we discuss the design of the PMCS, VC, and mechanism control interfaces, and how the IC can use them to configure the behavior of these sub-systems during an observation. We also discuss the interface to TRADS and how it is used as a common time base in each of these sub-systems. We present our preliminary results of the system performance against known instrument use cases.

  11. RAB-5 Controls the Cortical Organization and Dynamics of PAR Proteins to Maintain C. elegans Early Embryonic Polarity

    PubMed Central

    Hyenne, Vincent; Tremblay-Boudreault, Thierry; Velmurugan, Ramraj; Grant, Barth D.; Loerke, Dinah; Labbé, Jean-Claude

    2012-01-01

    In all organisms, cell polarity is fundamental for most aspects of cell physiology. In many species and cell types, it is controlled by the evolutionarily conserved PAR-3, PAR-6 and aPKC proteins, which are asymmetrically localized at the cell cortex where they define specific domains. While PAR proteins define the antero-posterior axis of the early C. elegans embryo, the mechanism controlling their asymmetric localization is not fully understood. Here we studied the role of endocytic regulators in embryonic polarization and asymmetric division. We found that depleting the early endosome regulator RAB-5 results in polarity-related phenotypes in the early embryo. Using Total Internal Reflection Fluorescence (TIRF) microscopy, we observed that PAR-6 is localized at the cell cortex in highly dynamic puncta and depleting RAB-5 decreased PAR-6 cortical dynamics during the polarity maintenance phase. Depletion of RAB-5 also increased PAR-6 association with clathrin heavy chain (CHC-1) and this increase depended on the presence of the GTPase dynamin, an upstream regulator of endocytosis. Interestingly, further analysis indicated that loss of RAB-5 leads to a disorganization of the actin cytoskeleton and that this occurs independently of dynamin activity. Our results indicate that RAB-5 promotes C. elegans embryonic polarity in both dynamin-dependent and -independent manners, by controlling PAR-6 localization and cortical dynamics through the regulation of its association with the cell cortex and the organization of the actin cytoskeleton. PMID:22545101

  12. Polarization-controlled spin reorientation transition and resistive switching in ferromagnetic-ferroelectric nanostructures and tunnel junctions

    NASA Astrophysics Data System (ADS)

    Pertsev, N. A.; Viaud, G.; Dkhil, B.

    2014-07-01

    A spin reorientation transition (SRT) induced in a ferromagnetic nanolayer by the polarization switching in an adjoining ferroelectric film or bulk crystal is described theoretically. It is shown that such a polarization-controlled SRT can be realized in a narrow range of the nanolayer thicknesses only. Our calculations allowing for the polarization-dependent interfacial magnetic anisotropy predict that this "thickness window" is located between two threshold thicknesses, at which a size-induced SRT takes place in the ferromagnetic nanolayer at two different directions of the ferroelectric polarization. Importantly, the polarization-controlled SRT manifests itself in the resistance switching occurring in multiferroic tunnel junctions (MFTJs), where an ultrathin ferroelectric barrier is embedded between a ferromagnetic electrode with controllable magnetization and an electrode with a fixed magnetization. Using Fe/BaTiO3/Fe junctions as a representative example, we demonstrate that such MFTJs can be employed as electric-write nanoscale memory cells with reliable nondestructive readout and high thermal stability of information storage.

  13. Polarization controlled deep sub-wavelength periodic features written by femtosecond laser on nanodiamond thin film surface

    SciTech Connect

    Kumar Kuntumalla, Mohan; Srikanth, Vadali V. S. S.; Rajamudili, Kuladeep; Rao Desai, Narayana

    2014-04-21

    Deep sub-wavelength (?/??=??0.22) periodic features are induced uniformly on a nanodiamond (ND) thin film surface using femtosecond (fs) laser irradiation (pulse duration?=??110 fs and central wavelength of ?800?nm). The topography of the surface features is controlled by the laser polarization. Orientation of features is perpendicular to laser polarization. Periodicity (spatial periodicity of?polarization controlled surface plasmon-fs laser coupling mechanism prompting the interaction between fs laser and solid matter (here ND thin film) which in turn is resulting in the periodic surface features. Scanning electron microscopy in conjunction with micro Raman scattering, X-ray diffraction, and atomic force microscopy are carried out to extract surface morphology and phase information of the laser irradiated regions. This work demonstrates an easy and efficient surface fabrication technique.

  14. Polarization controlled deep sub-wavelength periodic features written by femtosecond laser on nanodiamond thin film surface

    NASA Astrophysics Data System (ADS)

    Kumar Kuntumalla, Mohan; Rajamudili, Kuladeep; Rao Desai, Narayana; Srikanth, Vadali V. S. S.

    2014-04-01

    Deep sub-wavelength (?/? = ˜0.22) periodic features are induced uniformly on a nanodiamond (ND) thin film surface using femtosecond (fs) laser irradiation (pulse duration = ˜110 fs and central wavelength of ˜800 nm). The topography of the surface features is controlled by the laser polarization. Orientation of features is perpendicular to laser polarization. Periodicity (spatial periodicity of < ?/4) of the surface features is less than the laser wavelength. This work gives an experimental proof of polarization controlled surface plasmon-fs laser coupling mechanism prompting the interaction between fs laser and solid matter (here ND thin film) which in turn is resulting in the periodic surface features. Scanning electron microscopy in conjunction with micro Raman scattering, X-ray diffraction, and atomic force microscopy are carried out to extract surface morphology and phase information of the laser irradiated regions. This work demonstrates an easy and efficient surface fabrication technique.

  15. Distinct Roles for Two G?–G? Interfaces in Cell Polarity Control by a Yeast Heterotrimeric G Protein

    PubMed Central

    Strickfaden, Shelly C.

    2008-01-01

    Saccharomyces cerevisiae mating pheromones trigger dissociation of a heterotrimeric G protein (G???) into G?-guanosine triphosphate (GTP) and G??. The G?? dimer regulates both mitogen-activated protein (MAP) kinase cascade signaling and cell polarization. Here, by independently activating the MAP kinase pathway, we studied the polarity role of G?? in isolation from its signaling role. MAP kinase signaling alone could induce cell asymmetry but not directional growth. Surprisingly, active G??, either alone or with G?-GTP, could not organize a persistent polarization axis. Instead, following pheromone gradients (chemotropism) or directional growth without pheromone gradients (de novo polarization) required an intact receptor–G??? module and GTP hydrolysis by G?. Our results indicate that chemoattractant-induced cell polarization requires continuous receptor–G??? communication but not modulation of MAP kinase signaling. To explore regulation of G?? by G?, we mutated G? residues in two structurally distinct G?–G? binding interfaces. Polarity control was disrupted only by mutations in the N-terminal interface, and not the Switch interface. Incorporation of these mutations into a G?–G? fusion protein, which enforces subunit proximity, revealed that Switch interface dissociation regulates signaling, whereas the N-terminal interface may govern receptor–G??? coupling. These findings raise the possibility that the G??? heterotrimer can function in a partially dissociated state, tethered by the N-terminal interface. PMID:17978098

  16. Optimization of mode numbers of VCSELs for small-cell backhaul applications

    NASA Astrophysics Data System (ADS)

    Lu, I.-Cheng; Wei, Chia-Chien; Shi, Jin-Wei; Chen, Hsing-Yu; Tsai, Sheng-Fan; Hsu, Dar-Zu; Wei, Zhi-Rui; Wun, Jhih-Min; Chen, Jyehong

    2015-07-01

    This paper reports optical orthogonal frequency-division multiplexing (OFDM) transmission using 850 nm Zn-diffusion Vertical-Cavity Surface-Emitting Lasers (VCSELs) and multimode fiber (MMF) for small-cell backhaul applications. We also investigated the influence of side mode suppression ratio (SMSR) on the performance of OFDM modulation. By further optimizing the Zn-diffusion conditions and oxide aperture size, a high-power (6.7 mW) SM (SMSR>30 dB) VCSEL is demonstrated. By using OFDM modulation and bit-loading algorithm, record-high BRDP (91 Gb/s km) at 26 Gb/s transmission under FEC threshold (bit error rate (BER)<3.8×10-3) across 3.5 km OM4 fiber has been successfully demonstrated.

  17. 1W frequency-doubled VCSEL-pumped blue laser with high pulse energy

    NASA Astrophysics Data System (ADS)

    Van Leeuwen, Robert; Chen, Tong; Watkins, Laurence; Xu, Guoyang; Seurin, Jean-Francois; Wang, Qing; Zhou, Delai; Ghosh, Chuni

    2015-02-01

    We report on a Q-switched VCSEL side-pumped 946 nm Nd:YAG laser that produces high average power blue light with high pulse energy after frequency doubling in BBO. The gain medium was water cooled and symmetrically pumped by three 1 kW 808 nm VCSEL pump modules. More than 1 W blue output was achieved at 210 Hz with 4.9 mJ pulse energy and at 340 Hz with 3.2 mJ pulse energy, with 42% and 36% second harmonic conversion efficiency respectively. Higher pulse energy was obtained at lower repetition frequencies, up to 9.3 mJ at 70 Hz with 52% conversion efficiency.

  18. Low chirp and high-speed operation of transverse coupled cavity VCSEL

    NASA Astrophysics Data System (ADS)

    Hu, Shanting; Ahmed, Moustafa; Bakry, Ahmed; Koyama, Fumio

    2015-09-01

    We present the modeling on the modulation bandwidth and frequency chirp of transverse-coupled-cavity vertical-cavity surface-emitting lasers (VCSELs), which enable us to tailor the transfer function of intensity and frequency modulations thanks to an optical feedback effect. The simulation shows the 3-dB-modulation bandwidth can be doubled and the chirp can be reduced by a factor of more than three. These improvements could be explained by an increase in differential net gain in coupled cavities. The result shows a possibility of high-speed and low-chirp operations of transverse coupled cavity VCSELs for higher data rates and longer link lengths of single-mode fiber transmissions.

  19. 1074 IEEE TRANSACTIONS ON NANOTECHNOLOGY, VOL. 13, NO. 6, NOVEMBER 2014 A Circuit Synthesis Flow for Controllable-Polarity

    E-print Network

    De Micheli, Giovanni

    1074 IEEE TRANSACTIONS ON NANOTECHNOLOGY, VOL. 13, NO. 6, NOVEMBER 2014 A Circuit Synthesis Flow--CAD, controllable-polarity field-effect transistors (FETs), double-gate (DG) FETs, logic synthesis, nanotechnology, silicon nanowires. I. INTRODUCTION AS we advance into the era of nanotechnology, semicon- ductor devices

  20. Microtubule Polarity and Dynamics in the Control of Organelle Positioning, Segregation, and Cytokinesis in the Trypanosome Cell Cycle

    E-print Network

    Schnaufer, Achim

    Microtubule Polarity and Dynamics in the Control of Organelle Positioning, Segregation is cen- tral to cell cycle events such as organelle positioning, segregation, mitosis, and cytokinesis to be at the posterior end of the cell. Measurements of organelle positions through the cell cycle reveal a high degree

  1. Pulse width shaping of passively mode-locked soliton fiber laser via polarization control in carbon nanotube saturable absorber.

    PubMed

    Jeong, Hwanseong; Choi, Sun Young; Rotermund, Fabian; Yeom, Dong-Il

    2013-11-01

    We report the continuous control of the pulse width of a passively mode-locked fiber laser via polarization state adjustment in a single-walled carbon nanotube saturable absorber (SWCNT-SA). The SWCNT, coated on the side-polished fiber, was fabricated with optimized conditions and used for stable mode-locking of the fiber laser without Q-switching instabilities for any polarization state of the laser intra-cavity. The 3-dB spectral bandwidth of the mode-locked pulses can be continuously tuned from 1.8 nm to 8.5 nm with the polarization control for a given laser cavity length and applied pump power. A pulse duration varying from 470 fs to 1.6 ps was also observed with a change in the spectral bandwidth. The linear and the nonlinear transmission properties of the SA were analyzed, and found to exhibit different modulation depths depending on the input polarization state in the SA. The largest modulation depth of the SA was observed at the polarization state of the transverse electric mode that delivers shortest pulses at the laser output. PMID:24216924

  2. Myeloid mineralocorticoid receptor controls macrophage polarization and cardiovascular hypertrophy and remodeling in mice

    PubMed Central

    Usher, Michael G.; Duan, Sheng Zhong; Ivaschenko, Christine Y.; Frieler, Ryan A.; Berger, Stefan; Schütz, Günther; Lumeng, Carey N.; Mortensen, Richard M.

    2010-01-01

    Inappropriate excess of the steroid hormone aldosterone, which is a mineralocorticoid receptor (MR) agonist, is associated with increased inflammation and risk of cardiovascular disease. MR antagonists are cardioprotective and antiinflammatory in vivo, and evidence suggests that they mediate these effects in part by aldosterone-independent mechanisms. Here we have shown that MR on myeloid cells is necessary for efficient classical macrophage activation by proinflammatory cytokines. Macrophages from mice lacking MR in myeloid cells (referred to herein as MyMRKO mice) exhibited a transcription profile of alternative activation. In vitro, MR deficiency synergized with inducers of alternatively activated macrophages (for example, IL-4 and agonists of PPAR? and the glucocorticoid receptor) to enhance alternative activation. In vivo, MR deficiency in macrophages mimicked the effects of MR antagonists and protected against cardiac hypertrophy, fibrosis, and vascular damage caused by L-NAME/Ang II. Increased blood pressure and heart rates and decreased circadian variation were observed during treatment of MyMRKO mice with L-NAME/Ang II. We conclude that myeloid MR is an important control point in macrophage polarization and that the function of MR on myeloid cells likely represents a conserved ancestral MR function that is integrated in a transcriptional network with PPAR? and glucocorticoid receptor. Furthermore, myeloid MR is critical for blood pressure control and for hypertrophic and fibrotic responses in the mouse heart and aorta. PMID:20697155

  3. Simulation of Optical Resonators for Vertical-Cavity Surface-Emitting Lasers (vcsel)

    NASA Astrophysics Data System (ADS)

    Mansour, Mohy S.; Hassen, Mahmoud F. M.; El-Nozahey, Adel M.; Hafez, Alaa S.; Metry, Samer F.

    2010-04-01

    Simulation and modeling of the reflectivity and transmissivity of the multilayer DBR of VCSEL, as well as inside the active region quantum well are analyzed using the characteristic matrix method. The electric field intensity distributions inside such vertical-cavity structure are calculated. A software program under MATLAB environment is constructed for the simulation. This study was performed for two specific Bragg wavelengths 980 nm and 370 nm for achieving a resonant periodic gain (RPG)

  4. Proton Irradiation Effects in Oxide-Confined Vertical Cavity Surface Emitting Laser (VCSEL) Diodes

    SciTech Connect

    Armendariz, M.G.; Barnes, C.E.; Choquette, K.D.; Guertin, S.; Hash, G.L.; Schwank, J.R.; Swift, G.M.

    1999-03-11

    Recent space experience has shown that the use of commercial optocouplers can be problematic in spacecraft, such as TOPEX/Poseidon, that must operate in significant radiation environments. Radiation--induced failures of these devices have been observed in space and have been further documented at similar radiation doses in the laboratory. The ubiquitous use of optocouplers in spacecraft systems for a variety of applications, such as electrical isolation, switching and power transfer, is indicative of the need for optocouplers that can withstand the space radiation environment. In addition, the distributed nature of their use implies that it is not particularly desirable to shield optocouplers for use in radiation environments. Thus, it will be important for the space community to have access to radiation hardened/tolerant optocouplers. For many microelectronic and photonic devices, it is difficult to achieve radiation hardness without sacrificing performance. However, in the case of optocouplers, one should be able to achieve both superior radiation hardness and performance for such characteristics as switching speed, current transfer ratio (CTR), minimum power usage and array power transfer, if standard light emitting diodes (LEDs), such as those in the commercial optocouplers mentioned above, are avoided, and VCSELs are employed as the emitter portion of the optocoupler. The physical configuration of VCSELs allows one to achieve parallel use of an array of devices and construct a multichannel optocoupler in the standard fashion with the emitters and detectors looking at each other. In addition, detectors similar in structure to the VCSELs can be fabricated which allows bidirectional functionality of the optocoupler. Recent discussions suggest that VCSELs will enjoy widespread applications in the telecommunications and data transfer fields.

  5. Progress on high-power high-brightness VCSELs and applications

    NASA Astrophysics Data System (ADS)

    Zhou, Delai; Seurin, Jean-Francois; Xu, Guoyang; Zhao, Pu; Xu, Bing; Chen, Tong; Van Leeuwen, Robert; Matheussen, Joseph; Wang, Qing; Ghosh, Chuni

    2015-03-01

    Vertical-cavity surface-emitting lasers (VCSELs) are attractive for many pumping and direct-diode applications due to combined advantages in low cost, high reliability, narrow and thermally stable spectrum, high power scalability, and easy system integration, etc. We report our progress on electrically pumped, GaAs-based, high- power high-brightness VCSELs and 2D arrays in the infrared wavelength range. At 976nm, over 5.5W peak CW output and 60% peak power conversion efficiency (PCE) were demonstrated with 225um oxide-confined device. For 5x5mm arrays, peak PCE of 54% and peak power of >450W at 976nm, peak PCE of 46% and peak power of >110W at 808nm were achieved respectively under QCW conditions. External cavity configuration was used to improve the VCSEL brightness. Single mode output of 280mW and 37% PCE were realized from 80um device. For large 325um device, we obtained single mode (M2=1.1) CW output of 2.1W, corresponding to a brightness of 160MW/cm2*sr. Three major areas of applications using such VCSELs are discussed: 1. High brightness fiber output; 2. High power, high efficiency green lasers from 2nd harmonic generation. 3.34W green output with 21.2% PCE were achieved; 3. Pumping solid state lasers for high energy pulse generation. We have demonstrated Q-switched pulses with 16.1mJ at 1064nm and 4.9mJ with 1W average power at 473nm.

  6. Possible Composition of Martian Polar Caps and Controls on Ice-Cap Behavior

    NASA Astrophysics Data System (ADS)

    Kargel, J. S.

    1998-01-01

    David Fisher asked "if martian polar caps flow." Are martian polar caps akin to Earth's polar glacial ice sheets, or are they immobile? Though certain dynamical differences are obvious, it is unknown whether similarities in ice tectonics may also exist. The question bears not only on modem martian polar processes, but perhaps on hypothesized glacial processes elsewhere on Mars in the geologic past. The rheological properties and tectonics of martian polar caps also pertain to the possibility that liquids may have existed beneath the polar caps in the past, or even now, and to prospects for life in possible lakes beneath the ice caps. The cold martian polar surface temperatures and the lower martian gravity suggest a reduced propensity of martian polar ice deposits to deform under their own weight. The greater accumulation timescales of the martian polar caps compared to Earth's also mean that more time has been available for accumulated deformation, possibly offsetting the effects of colder temperatures and lower gravity on Mars. Further complicating our understanding is that the martian polar caps may not be made purely of ordinary water ice - CO2 is another possible major constituent; the rheological and melting behavior may be very different from what we are accustomed to dealing with on Earth.

  7. Solar wind control of the open magnetosphere: Comparison of GGS/polar images and theory

    NASA Astrophysics Data System (ADS)

    Urquhart, Andrew Lee

    This investigation explores the connection between the open polar cap magnetic flux ?PCF and interplanetary conditions. ? PCF is determined from GGS/Polar VIS Earth Camera far ultraviolet observations of the aurora borealis. Observations from the GGS/Wind SWE and MFI instruments are used to characterize the interplanetary conditions. Additional observations from the IMP-8 PLA and MAG instruments are used to evaluate solar wind propagation time delay estimation methods so that the GGS/Wind observations can be better associated with the GGS/Polar observations. This allows the GGS/Wind observations to be used to estimate the polar cap potential ?PCP values associated with the GGS/Polar ?PCF values. Statistical methods are applied to determine a proxy relationship between ?PCP and ?PCF. The Rice Field Model (RFM) is modified to accept ? PCF as a configuration parameter, and RFM polar caps are produced using ? PCF determined both directly from the GGS/Polar images and by the proxy relationship from the GGS/Wind data. The RFM is able to produce polar caps with the same areas and open magnetic fluxes as the GGS/Polar observations, but the agreement in the polar cap shapes and locations leaves opportunities for further improvements.

  8. Bidirectional hybrid PM-based RoF and VCSEL-based VLLC system.

    PubMed

    Li, Chung-Yi; Lu, Hai-Han; Chang, Ching-Hung; Lin, Chun-Yu; Wu, Po-Yi; Zheng, Jun-Ren; Lin, Chia-Rung

    2014-06-30

    A bidirectional hybrid phase modulation (PM)-based radio-over-fiber (RoF) and vertical cavity surface emitting laser (VCSEL)-based visible laser light communication (VLLC) systems employing injection-locked VCSEL-based PM-to-intensity modulation (IM) converters and optical interleavers (ILs) is proposed and demonstrated. To be the first one of using injection-locked VCSEL-based PM-to-IM converters and optical ILs in such bidirectional hybrid RoF and VLLC systems, the downstream light is successfully phase-remodulated with RoF signal for up-link transmission. Through a serious investigation in systems, bit error rate (BER) and eye diagram perform brilliantly over a 40-km single-mode fiber (SMF) transport and a 12-m free-space transmission. Such a bidirectional hybrid RoF and VLLC system would be very attractive for the integration of fiber backbone and in-door networks to provide broadband integrated services, including Internet and telecommunication services. PMID:24977870

  9. Development of a Compact Optical-MEMS Scanner with Integrated VCSEL Light Source and Diffractive Optics

    SciTech Connect

    Krygowski, Thomas W.; Reyes, David; Rodgers, M. Steven; Smith, James H.; Warren, Mial; Sweatt, William; Blum-Spahn, Olga; Wendt, Joel R.; Asbill, Randy

    1999-06-30

    In this work the design and initial fabrication results are reported for the components of a compact optical-MEMS laser scanning system. This system integrates a silicon MEMS laser scanner, a Vertical Cavity Surface Emitting Laser (VCSEL) and passive optical components. The MEMS scanner and VCSEL are mounted onto a fused silica substrate which serves as an optical interconnect between the devices. Two Diffractive Optical Elements (DOEs) are etched into the fused silica substrate to focus the VCSEL beam and increase the scan range. The silicon MEMS scanner consists of an actuator that continuously scans the position of a large polysilicon gold-coated shuttle containing a third DOE. Interferometric measurements show that the residual stress in the 500 {micro}m x 1000 {micro}m shuttle is extremely low, with a maximum deflection of only 0.18{micro}m over an 800 {micro}m span for an unmetallized case and a deflection of 0.56{micro}m for the metallized case. A conservative estimate for the scan range is {approximately}{+-}4{degree}, with a spot size of about 0.5 mm, producing 50 resolvable spots. The basic system architecture, optical and MEMS design is reported in this paper, with an emphasis on the design and fabrication of the silicon MEMS scanner portion of the system.

  10. Two dimensional analysis of finite size high-contrast gratings for applications in VCSELs.

    PubMed

    Liu, Anjin; Hofmann, Werner; Bimberg, Dieter

    2014-05-19

    2-dimensional simulations of high-contrast gratings (HCGs) of finite size are carried out, targeting at their applications in vertical-cavity surface-emitting lasers (VCSELs). Finite HCGs show a very different behavior from infinite grating ones. The reflectivity of a finite HCG strongly depends on the HCG size and the source size. Our simulation results predict finite reflectivity and transmission values, well consistent with reported experimental results. The band of high reflectivity (>99.5%) of finite HCGs is less broad as compared to the infinite case. Losses into a guided mode excited in the HCG plane are identified as being at the root. This guided mode is excited due to the nonzero angular components in the finite source size, and greatly enhances the transmission and the light leakage from the slab. In addition, the simulation results show that the details of the finite HCG can shape the output beam, whilst a Gaussian-like reflected wave is typically achieved. Our simulations can explain the current discrepancies between numerical predictions of reflectivities approaching 100% and working HCG-VCSELs showing finite reflectivities and nearly Gaussian-like output. Consequently, our analysis of finite HCGs is indispensable for HCG-VCSEL design. PMID:24921302

  11. Temperature characteristics of surface micromachined MEMS-VCSEL with large tuning range.

    PubMed

    Gierl, C; Gründl, T; Paul, S; Zogal, K; Haidar, M T; Meissner, P; Amann, M-C; Küppers, F

    2014-06-01

    Several Applications for tunable laser diodes have strict constraints in terms of overall power consumption. Furthermore, the implementation in harsh environments with large temperature fluctuations is necessary. Due to the constraint in power consumption, the application of active cooling might not be an option. For this reason we investigate the temperature characteristics of an electrically pumped MEMS-VCSEL with wide continuous wavelength tuning. For the first time, a mode hop free single mode (side mode suppression ratio (SMSR) > 40dB) tuning range of 45nm at 70°C is demonstrated with a MEMS-VCSEL. An increase of the tuning range from 85nm at 20°C to 92nm at 40°C is measured and explained. In contrast to fixed wavelength VCSEL, the investigated device shows a negative temperature induced wavelength shift of -4.5nmK(-1), which is caused by the MEMS-mirror. At 1560nm, the fibre-coupled optical output power is above 0.6mW over the entire temperature range between 20°C to 70°C and shows a maximum of > 3mW at 20°C. PMID:24921503

  12. Fabrication, Packaging, and Performance of VCSELs and Photodetectors for Space Applications

    SciTech Connect

    Armendariz, M.G.; Briggs, R.D.; Choquette, K.D.; Geib, K.M.; Serkland, D.K.

    1999-03-09

    Optocouplers are used for a variety of applications aboard spacecraft including electrical isolation, switching and power transfer. Commercially available light emitting diode (LED)-based optocouplers have experienced severe degradation of light output due to extensive displacement damage occurring in the semiconductor lattice caused by energetic proton bombardment. A new optocoupler has been designed and fabricated which utilizes vertical cavity surface emitting laser (VCSEL) and resonant cavity photodetector (RCPD) technologies for the optocoupler emitter and detector, respectively. Linear arrays of selectively oxidized GaAs/AlGaAs VCSELS and RCPDS, each designed to operate at a wavelength of 850nm, were fabricated using an airbridge contacting scheme. The airbridged contacts were designed to improve packaging yields and device reliability by eliminating the use of a polyimide planarizing layer which provided poor adhesion to the bond pad metallization. Details of the airbridged optocoupler fabrication process are reported. Discrete VCSEL and RCPD devices were characterized at temperatures between {minus}100 to 100 C. Devices were packaged in a face-to-face configuration to form a single channel optocoupler and its performance was evaluated under conditions of high-energy proton bombardment.

  13. High-speed 850 and 980 nm VCSELs for high-performance computing applications

    NASA Astrophysics Data System (ADS)

    Mutig, Alex; Moser, Philip; Lott, James A.; Wolf, Philip; Hofmann, Werner; Ledentsov, Nikolay N.; Bimberg, Dieter

    2011-12-01

    The ever growing demand for more bandwidth in high-performance computing (HPC) applications leads to a continuous replacement of traditional copper-based links by optical interconnects at ever shorter transmission distances. However, this trend results in a more stringent performance requirements for laser light sources utilized in new generations of optical interconnects in respect to single channel speed, packaging density, power consumption and temperature stability, to make the technology competitive and commercially viable. Vertical cavity surface emitting lasers operating at different wavelengths, e. g. 850 or 980 nm, represent one possible solution for the short distance high density interconnects in HPC applications. Here we present ultra-high speed highly temperature stable 980 nm VCSELs operating error-free at the record high bit rate of 44 Gbit/s at room temperature and 38 Gbit/s at 85 °C for future interand intra-chip, and module-to-module optical links. Next we present high speed extremely energy efficient 850 nm VCSELs with record low energy consumptions of only 83 fJ/bit while operating at 17 Gbit/s and of only 117 fJ/bit at 25 Gbit/s. Our VCSELs enable ecologically sound and economically practical HPC designs.

  14. Wideband Electrically-Pumped 1050 nm MEMS-Tunable VCSEL for Ophthalmic Imaging

    PubMed Central

    John, Demis D.; Burgner, Christopher B.; Potsaid, Benjamin; Robertson, Martin E.; Lee, Byung Kun; Choi, Woo Jhon; Cable, Alex E.; Fujimoto, James G.; Jayaraman, Vijaysekhar

    2015-01-01

    In this paper, we present a 1050 nm electrically-pumped micro-electro-mechanically-tunable vertical-cavity-surface-emitting-laser (MEMS-VCSEL) with a record dynamic tuning bandwidth of 63.8 nm, suitable for swept source optical coherence tomography (SS-OCT) imaging. These devices provide reduced cost & complexity relative to previously demonstrated optically pumped devices by obviating the need for a pump laser and associated hardware. We demonstrate ophthalmic SS-OCT imaging with the electrically-pumped MEMS-VCSEL at a 400 kHz axial scan rate for wide field imaging of the in vivo human retina over a 12 mm × 12 mm field and for OCT angiography of the macula over 6 mm × 6 mm & 3 mm × 3 mm fields to show retinal vasculature and capillary structure near the fovea. These results demonstrate the feasibility of electrically pumped MEMS-VCSELs in ophthalmic instrumentation, the largest clinical application of OCT. In addition, we estimate that the 3 dB coherence length in air is 225 meters ± 51 meters, far greater than required for ophthalmic SS-OCT and suggestive of other distance ranging applications. PMID:26594089

  15. Polarization control of high order harmonics in the EUV photon energy range.

    PubMed

    Vodungbo, Boris; Barszczak Sardinha, Anna; Gautier, Julien; Lambert, Guillaume; Valentin, Constance; Lozano, Magali; Iaquaniello, Grégory; Delmotte, Franck; Sebban, Stéphane; Lüning, Jan; Zeitoun, Philippe

    2011-02-28

    We report the generation of circularly polarized high order harmonics in the extreme ultraviolet range (18-27 nm) from a linearly polarized infrared laser (40 fs, 0.25 TW) focused into a neon filled gas cell. To circularly polarize the initially linearly polarized harmonics we have implemented a four-reflector phase-shifter. Fully circularly polarized radiation has been obtained with an efficiency of a few percents, thus being significantly more efficient than currently demonstrated direct generation of elliptically polarized harmonics. This demonstration opens up new experimental capabilities based on high order harmonics, for example, in biology and materials science. The inherent femtosecond time resolution of high order harmonic generating table top laser sources renders these an ideal tool for the investigation of ultrafast magnetization dynamics now that the magnetic circular dichroism at the absorption M-edges of transition metals can be exploited. PMID:21369265

  16. Catalyst-site-controlled coordination polymerization of polar vinyl monomers to highly syndiotactic polymers.

    PubMed

    Zhang, Yuetao; Ning, Yalan; Caporaso, Lucia; Cavallo, Luigi; Chen, Eugene Y-X

    2010-03-01

    This contribution reports a combined synthetic, kinetic, mechanistic, and theoretical/computational study of the recently discovered catalyst-site-controlled coordination polymerization of polar vinyl monomers [such as methyl methacrylate (MMA) and N,N-dimethylacrylamide (DMAA)] into highly syndiotactic polymers. Among the 12 C(s)-ligated ansa-cyclopentadienyl (Cp)-R(2)E(C,Si)-fluorenyl (Flu) group 4 metallocene catalyst systems examined-which varied in metal center, anion structure, bridging atom and substituents, and ligand substitution pattern-cationic ansa-metallocene ester enolate catalyst 6(+)[B(C(6)F(5))(4)](-), derived from the activation of the precatalyst [Ph(2)C(Cp)(2,7-(t)Bu(2)-Flu)]Zr[OC(O(i)Pr)=CMe(2)](2) with [Ph(3)C][B(C(6)F(5))(4)], stood out as the best catalyst in all aspects of the MMA polymerization at room temperature, including the highest activity (1554 h(-1) TOF), efficiency (98% I*), syndiotacticity (94% rr), and control (predicted number-average molecular weight and 1.14 molecular weight distribution). Kinetic and mechanistic results are consistent with a catalyst-site-controlled, monometallic coordination-addition mechanism, involving fast intramolecular addition within the catalyst-monomer complex leading to the resting eight-membered ester enolate chelate, followed by the rate-limiting ring-opening of the chelate to regenerate the active species. This work has also uncovered several unique features of this polymerization system that are in marked contrast to the propylene polymerization by analogous C(s)-ligated cationic alkyl catalysts: a constant syndiotacticity of PMMA produced over a wide polymerization temperature range (i.e., from 0 degrees C, 94% rr to 25 degrees C, 94% rr to 50 degrees C, 93% rr); insensitivity of its high activity, degree of control, and stereoselectivity to solvent polarity and structure of weakly coordinating anions; and deviation from a pure site-control mechanism at high [MMA]/[catalyst] ratios. Computational results provide theoretical support for the proposed monomer-assisted, catalyst-site epimerization, after an enantiofacial mistake, to a thermodynamically more stable resting state, which accounts for the observed higher than expected [mr] contents based on a pure site-controlled mechanism. DFT calculations rationalize why the Ph(2)C< bridged catalyst 6 exhibits higher stereoselectivity than other catalysts with the Me(2)C< or Me(2)Si< bridge: the bridge rigidity pushes the eta(3)-bound Flu ligand closer to the growing chain and the monomer, thereby increasing DeltaE(stereo) between the competing transition states for the addition of a monomer molecule to the opposite (correct and wrong) enantiofaces of the enolate growing chain. The relative polymerization activity of this catalyst series is shown to correlate with the relative energetics of the back-biting of the penultimate unit and ion-pair formation. PMID:20121281

  17. Electron ionization and spin polarization control of Fe atom adsorbed graphene irradiated by a femtosecond laser

    NASA Astrophysics Data System (ADS)

    Yu, Dong; Jiang, Lan; Wang, Feng; Li, Xin; Qu, Liangti; Lu, Yongfeng

    2015-10-01

    We investigate the structural properties and ionized spin electrons of an Fe-graphene system, in which the time-dependent density functional theory (TDDFT) within the generalized gradient approximation is used. The electron dynamics, including electron ionization and ionized electron spin polarization, is described for Fe atom adsorbed graphene under femtosecond laser irradiation. The theoretical results show that the electron ionization and ionized electron spin polarization are sensitive to the laser parameters, such as the incident angle and the peak intensity. The spin polarization presents the maximum value under certain laser parameters, which may be used as a source of spin-polarized electrons.

  18. The planar cell polarity effector protein Wdpcp (Fritz) controls epithelial cell cortex dynamics via septins and actomyosin

    PubMed Central

    Park, Tae Joo; Kim, Su Kyoung; Wallingford, John B.

    2015-01-01

    Planar cell polarity (PCP) signaling controls polarized behaviors in diverse tissues, including the collective cell movements of gastrulation and the planar polarized beating of motile cilia. A major question in PCP signaling concerns the mechanisms linking this signaling cascade with more general cytoskeletal elements to drive polarized behavior. Previously, we reported that the PCP effector protein Wdpcp (formerly known as Fritz) interacts with septins and is critical for collective cell migration and cilia formation. Here, we report that Wdpcp is broadly involved in maintaining cortical tension in epithelial cells. In vivo 3D time-lapse imaging revealed that Wdpcp is necessary for basolateral plasma membrane stability in epithelial tissues, and we further show that Wdpcp controls cortical septin localization to maintain cortical rigidity in mucociliary epithelial cells. Finally, we show that Wdpcp acts via actomyosin to maintain balanced cortical tension in the epithelium. These data suggest that, in addition to its role in controlling plasma membrane dynamics in collective mesenchymal cell movements, Wdpcp is also essential for normal cell cortex stability during epithelial homeostasis. PMID:25436430

  19. Equilibrium polarization of ultrathin PbTiO{<_3} with surface compensation controlled by oxygen partial pressure.

    SciTech Connect

    Highland, M. J.; Fister, T. T.; Fong, D. D.; Fuoss, P. H.; Thompson, C.; Eastman, J. A.; Streiffer, S. K.; Stephenson, G. B.

    2011-01-01

    We present a synchrotron x-ray study of the equilibrium polarization structure of ultrathin PbTiO{sub 3} films on SrRuO{sub 3} electrodes epitaxially grown on SrTiO{sub 3} (001) substrates, as a function of temperature and the external oxygen partial pressure (pO{sub 2}) controlling their surface charge compensation. We find that the ferroelectric Curie temperature (T{sub c}) varies with pO{sub 2} and has a minimum at the intermediate pO{sub 2}, where the polarization below T{sub c} changes sign. The experiments are in qualitative agreement with a model based on Landau theory that takes into account the interaction of the phase transition with the electrochemical equilibria for charged surface species. The paraelectric phase is stabilized at intermediate pO2 when the concentrations of surface species are insufficient to compensate either polar orientation.

  20. Polarized linewidth-controllable double-trapping electromagnetically induced transparency spectra in a resonant plasmon nanocavity

    PubMed Central

    Wang, Luojia; Gu, Ying; Chen, Hongyi; Zhang, Jia-Yu; Cui, Yiping; Gerardot, Brian D.; Gong, Qihuang

    2013-01-01

    Surface plasmons with ultrasmall optical mode volume and strong near field enhancement can be used to realize nanoscale light-matter interaction. Combining surface plasmons with the quantum system provides the possibility of nanoscale realization of important quantum optical phenomena, including the electromagnetically induced transparency (EIT), which has many applications in nonlinear quantum optics and quantum information processing. Here, using a custom-designed resonant plasmon nanocavity, we demonstrate polarized position-dependent linewidth-controllable EIT spectra at the nanoscale. We analytically obtain the double coherent population trapping conditions in a double-? quantum system with crossing damping, which give two transparent points in the EIT spectra. The linewidths of the three peaks are extremely sensitive to the level spacing of the excited states, the Rabi frequencies and detunings of pump fields, and the Purcell factors. In particular the linewidth of the central peak is exceptionally narrow. The hybrid system may have potential applications in ultra-compact plasmon-quantum devices. PMID:24096943

  1. Control of the polarization of a vacuum-ultraviolet, high-gain, free-electron laser

    DOE PAGESBeta

    Allaria, Enrico; Diviacco, Bruno; Callegari, Carlo; Finetti, Paola; Mahieu, Benoît; Viefhaus, Jens; Zangrando, Marco; De Ninno, Giovanni; Lambert, Guillaume; Ferrari, Eugenio; et al

    2014-12-02

    The two single-pass, externally seeded free-electron lasers (FELs) of the FERMI user facility are designed around Apple-II-type undulators that can operate at arbitrary polarization in the vacuum ultraviolet-to-soft x-ray spectral range. Furthermore, within each FEL tuning range, any output wavelength and polarization can be set in less than a minute of routine operations. We report the first demonstration of the full output polarization capabilities of FERMI FEL-1 in a campaign of experiments where the wavelength and nominal polarization are set to a series of representative values, and the polarization of the emitted intense pulses is thoroughly characterized by three independentmore »instruments and methods, expressly developed for the task. The measured radiation polarization is consistently >90% and is not significantly spoiled by the transport optics; differing, relative transport losses for horizontal and vertical polarization become more prominent at longer wavelengths and lead to a non-negligible ellipticity for an originally circularly polarized state. The results from the different polarimeter setups validate each other, allow a cross-calibration of the instruments, and constitute a benchmark for user experiments.« less

  2. Control of the polarization of a vacuum-ultraviolet, high-gain, free-electron laser

    SciTech Connect

    Allaria, Enrico; Diviacco, Bruno; Callegari, Carlo; Finetti, Paola; Mahieu, Benoît; Viefhaus, Jens; Zangrando, Marco; De Ninno, Giovanni; Lambert, Guillaume; Ferrari, Eugenio; Buck, Jens; Ilchen, Markus; Vodungbo, Boris; Mahne, Nicola; Svetina, Cristian; Spezzani, Carlo; Di Mitri, Simone; Penco, Giuseppe; Trovó, Mauro; Fawley, William M.; Rebernik, Primoz R.; Gauthier, David; Grazioli, Cesare; Coreno, Marcello; Ressel, Barbara; Kivimäki, Antti; Mazza, Tommaso; Glaser, Leif; Scholz, Frank; Seltmann, Joern; Gessler, Patrick; Grünert, Jan; De Fanis, Alberto; Meyer, Michael; Knie, André; Moeller, Stefan P.; Raimondi, Lorenzo; Capotondi, Flavio; Pedersoli, Emanuele; Plekan, Oksana; Danailov, Miltcho B.; Demidovich, Alexander; Nikolov, Ivaylo; Abrami, Alessandro; Gautier, Julien; Lüning, Jan; Zeitoun, Philippe; Giannessi, Luca

    2014-12-02

    The two single-pass, externally seeded free-electron lasers (FELs) of the FERMI user facility are designed around Apple-II-type undulators that can operate at arbitrary polarization in the vacuum ultraviolet-to-soft x-ray spectral range. Furthermore, within each FEL tuning range, any output wavelength and polarization can be set in less than a minute of routine operations. We report the first demonstration of the full output polarization capabilities of FERMI FEL-1 in a campaign of experiments where the wavelength and nominal polarization are set to a series of representative values, and the polarization of the emitted intense pulses is thoroughly characterized by three independent instruments and methods, expressly developed for the task. The measured radiation polarization is consistently >90% and is not significantly spoiled by the transport optics; differing, relative transport losses for horizontal and vertical polarization become more prominent at longer wavelengths and lead to a non-negligible ellipticity for an originally circularly polarized state. The results from the different polarimeter setups validate each other, allow a cross-calibration of the instruments, and constitute a benchmark for user experiments.

  3. Control of the Polarization of a Vacuum-Ultraviolet, High-Gain, Free-Electron Laser

    NASA Astrophysics Data System (ADS)

    Allaria, Enrico; Diviacco, Bruno; Callegari, Carlo; Finetti, Paola; Mahieu, Benoît; Viefhaus, Jens; Zangrando, Marco; De Ninno, Giovanni; Lambert, Guillaume; Ferrari, Eugenio; Buck, Jens; Ilchen, Markus; Vodungbo, Boris; Mahne, Nicola; Svetina, Cristian; Spezzani, Carlo; Di Mitri, Simone; Penco, Giuseppe; Trovó, Mauro; Fawley, William M.; Rebernik, Primoz R.; Gauthier, David; Grazioli, Cesare; Coreno, Marcello; Ressel, Barbara; Kivimäki, Antti; Mazza, Tommaso; Glaser, Leif; Scholz, Frank; Seltmann, Joern; Gessler, Patrick; Grünert, Jan; De Fanis, Alberto; Meyer, Michael; Knie, André; Moeller, Stefan P.; Raimondi, Lorenzo; Capotondi, Flavio; Pedersoli, Emanuele; Plekan, Oksana; Danailov, Miltcho B.; Demidovich, Alexander; Nikolov, Ivaylo; Abrami, Alessandro; Gautier, Julien; Lüning, Jan; Zeitoun, Philippe; Giannessi, Luca

    2014-10-01

    The two single-pass, externally seeded free-electron lasers (FELs) of the FERMI user facility are designed around Apple-II-type undulators that can operate at arbitrary polarization in the vacuum ultraviolet-to-soft x-ray spectral range. Furthermore, within each FEL tuning range, any output wavelength and polarization can be set in less than a minute of routine operations. We report the first demonstration of the full output polarization capabilities of FERMI FEL-1 in a campaign of experiments where the wavelength and nominal polarization are set to a series of representative values, and the polarization of the emitted intense pulses is thoroughly characterized by three independent instruments and methods, expressly developed for the task. The measured radiation polarization is consistently >90 % and is not significantly spoiled by the transport optics; differing, relative transport losses for horizontal and vertical polarization become more prominent at longer wavelengths and lead to a non-negligible ellipticity for an originally circularly polarized state. The results from the different polarimeter setups validate each other, allow a cross-calibration of the instruments, and constitute a benchmark for user experiments.

  4. Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. http://pos.sissa.it Study of the radiation-hardness of VCSEL and PIN

    E-print Network

    Gan, K. K.

    -NonCommercial-ShareAlike Licence. http://pos.sissa.it Study of the radiation-hardness of VCSEL and PIN K.K. Gan1 , W. Fernando, H LHC with ten times higher luminosity. We study the radiation-hardness of VCSELs (Vertical in the data transmission upgrade. The optical power of VCSEL arrays decreases significantly after

  5. Controlled quantum key distribution with three-photon polarization-entangled states via the collective noise channel

    SciTech Connect

    Dong Li; Xiu Xiaoming; Gao Yajun; Yi, X. X.

    2011-10-15

    Using three-photon polarization-entangled GHZ states or W states, we propose controlled quantum key distribution protocols for circumventing two main types of collective noise, collective dephasing noise, or collective rotation noise. Irrespective of the number of controllers, a three-photon state can generate a one-bit secret key. The storage technique of quantum states is dispensable for the controller and the receiver, and it therefore allows performing the process in a more convenient mode. If the photon cost in a security check is disregarded, then the efficiency theoretically approaches unity.

  6. Photoelectron emission control with polarized light in plasmonic metal random structures

    SciTech Connect

    Word, R. C.; Fitzgerald, J.; Koenenkamp, R.

    2011-07-25

    We report on the possibility of switching the emission rate of photoelectrons by polarization changes in the plasmon excitation light. Photoelectron emission is strongly enhanced in the near-field of localized surface plasmons and occurs from areas with typical diameters of 20-70 nm. The underlying physical process involves excitation of a localized surface plasmon polariton with a femtosecond laser pulse, and a subsequent multi-photon photoemission process. The non-linearity of this process leads to a sharp polarization dependence that allows efficient switching of the emission. We demonstrate that a 90 deg. polarization change can result in on/off ratios of {approx}100 for electron emission.

  7. A method for polarization control and analysis on Bonse-Hart double-crystal USANS instruments

    NASA Astrophysics Data System (ADS)

    Littrell, Kenneth C.; Lee, Wai Tung

    2004-03-01

    The use of polarized beams and polarization analysis is an area of increasing interest to the small-angle neutron scattering (SANS) community. Since the angular acceptance of a DCD USANS instrument is very narrow, magnetic prisms can be exploited to select polarization. We compare two schemes by which this can be accomplished and describe how this method can be adapted for use on time-of-flight DCD USANS instruments. The wavelength dispersion of the prism can be used on steady-state instruments to select or suppress higher harmonics of the characteristic incident wavelength.

  8. VCSEL transmission at 10 Gb/s for 20 km single mode fiber WDM-PON without dispersion compensation or injection locking

    NASA Astrophysics Data System (ADS)

    Gibbon, T. B.; Prince, K.; Pham, T. T.; Tatarczak, A.; Neumeyr, C.; Rönneberg, E.; Ortsiefer, M.; Monroy, I. Tafur

    2011-01-01

    Vertical Cavity Surface Emitting Lasers (VCSELs) are extremely cost effective, energy efficient optical sources ideal for passive optical access networks. However, wavelength chirp and chromatic dispersion severely limit VCSEL performance at bit rates of 10 Gb/s and above. We experimentally show how off-center wavelength filtering of the VCSEL spectrum at an array waveguide grating can be used to mitigate the effect of chirp and the dispersion penalty. Transmission at 10 Gb/s VCSEL over 23.6 km of single mode fiber is experimentally demonstrated, with a dispersion penalty of only 2.9 dB. Simulated results are also presented which show that off-center wavelength filtering can extend the 10 Gb/s network reach from 11.7 km to 25.8 km for a 4 dB dispersion penalty. This allows for cheap and simple dispersion mitigation in next generation VCSEL-based optical access networks.

  9. Low-voltage, high-speed and compact electro-absorption modulator laterally integrated with 980-nm VCSEL.

    PubMed

    Dalir, Hamed; Takahashi, Yuta; Koyama, Fumio

    2014-10-20

    We present a compact electro-absorption slow-light modulator laterally-integrated with a 980-nm VCSEL. We figured out the small signal modulation response for different modulator lengths. While the 3-dB small-signal modulation bandwidth of conventional directly modulated VCSELs on the same epi-wafer structure was limited below 10 GHz, we obtained a modulation bandwidth over 21 GHz for a 30 µm long modulator. We also demonstrated large signal modulation up to 25 Gbps with a low driving voltage below 600 mV(pp) and an extinction ratio of 4 dB for the modulator length of 50 µm. Prospects of much higher speed (> 40 Gbps) were examined with reducing the size of the modulator. Also, the tapered waveguide coupling structure enables "quasi-unidirectional coupling", which reduces the optical feedback in a VCSEL from the integrated modulator. PMID:25401608

  10. A 20 km/80 Gbps bidirectional PON employing three-stage injection-locked VCSELs/NDFs/OBPFs

    NASA Astrophysics Data System (ADS)

    Ying, Cheng-Ling; Lu, Hai-Han; Li, Chung-Yi; Lin, Che-Yu; Wan, Zhi-Wei; Cheng, Chun-Jen

    2015-12-01

    A 20 km/80 Gbps bidirectional passive optical network (PON) employing three-stage, injection-locked, 1.55 ?m, vertical-cavity surface-emitting lasers (VCSELs), negative dispersion fibers (NDFs), and optical band-pass filters (OBPFs) is proposed and demonstrated. The three-stage injection-locked technique, which can greatly increase the frequency response of VCSELs, is thereby expected to provide excellent transmission performance in a bi-directional PON. To be the first one of employing directly modulated, three-stage injection-locked, 1.55 ?m, VCSELs; NDFs; and OBPFs results in excellent bit error rate (BER) performance, and clear eye diagrams are obtained for 20 km/80 Gbps, bidirectional PON applications. Such a novel bidirectional PON provides the advantage of a communication link for high data rates that could accelerate bidirectional PON deployment.

  11. SHG microscopy excited by polarization controlled beam for three-dimensional molecular orientation measurement

    NASA Astrophysics Data System (ADS)

    Yoshiki, K.; Hashimoto, M.; Araki, T.

    2006-08-01

    We have developed a second-harmonic-generation (SGH) microscope to observe the three-dimensional molecular orientation with three-dimensional high spatial resolution using a polarization mode converter. The mode converter consists of a parallel-aligned nematic-liquid-crystal spatial-light-modulator (PAL-SLM) and quarter-waveplates, and converts a incident linearly polarized beam to orthogonal linearly polarized beams or radially polarized beam. We combined the mode converter with SHG microscope to obtain the local information of the three-dimensional molecular orientation. We demonstrated the detection of three-dimensional molecular orientation of collagen fiber in human Achilles' tendon. For high precision three-dimensional molecular orientation measurement, we propose a technique to calibrate the dependence of SHG detection efficiencies on molecular orientation using a liposome.

  12. Control phase shift of spin-wave by spin-polarized current and its application in logic gates

    NASA Astrophysics Data System (ADS)

    Chen, Xiangxu; Wang, Qi; Liao, Yulong; Tang, Xiaoli; Zhang, Huaiwu; Zhong, Zhiyong

    2015-11-01

    We proposed a new ways to control the phase shift of propagating spin waves by applying a local spin-polarized current on ferromagnetic stripe. Micromagnetic simulation showed that a phase shift of about ? can be obtained by designing appropriate width and number of pinned magnetic layers. The ways can be adopted in a Mach-Zehnder-type interferometer structure to fulfill logic NOT gates based on spin waves.

  13. Molecular Cell, Vol. 7, 937947, May, 2001, Copyright 2001 by Cell Press Control of Cell Polarity and Chemotaxis by Akt/PKB

    E-print Network

    Firtel, Richard A.

    and Chemotaxis by Akt/PKB and PI3 Kinase through the Regulation of PAKa Tilton et al., 1997). Chemoattractant fusion is PI3K-dependent (Meili et al., (PKB or Akt) control cell polarity and chemotaxis, in 1999, 2000 mediate PAKa's subcellular localization, PAKa's regulates cell polarity and chemotaxis

  14. Monolithic high-index contrast grating: a material independent high-reflectance VCSEL mirror.

    PubMed

    G?bski, M; Dems, M; Szerling, A; Motyka, M; Marona, L; Kruszka, R; Urba?czyk, D; Walczakowski, M; Pa?ka, N; Wójcik-Jedli?ska, A; Wang, Q J; Zhang, D H; Bugajski, M; Wasiak, M; Czyszanowski, T

    2015-05-01

    In this paper we present an extensive theoretical and numerical analysis of monolithic high-index contrast grating, facilitating simple manufacture of compact mirrors for very broad spectrum of vertical-cavity surface-emitting lasers (VCSELs) emitting from ultraviolet to mid-infrared. We provide the theoretical background explaining the phenomenon of high reflectance in monolithic subwavelength gratings. In addition, by using a three-dimensional, fully vectorial optical model, verified by comparison with the experiment, we investigate the optimal parameters of high-index contrast grating enabling more than 99.99% reflectance in the diversity of photonic materials and in the broad range of wavelengths. PMID:25969259

  15. Phase-sensitive swept source OCT imaging of the human retina with a VCSEL light source

    PubMed Central

    Choi, WooJhon; Potsaid, Benjamin; Jayaraman, Vijaysekhar; Baumann, Bernhard; Grulkowski, Ireneusz; Liu, Jonathan J.; Lu, Chen D.; Cable, Alex E.; Huang, David; Duker, Jay S.; Fujimoto, James G.

    2013-01-01

    Despite the challenges in achieving high phase stability, Doppler swept source / Fourier domain OCT has advantages of less fringe washout and faster imaging speeds compared to spectral / Fourier domain detection. This manuscript demonstrates swept source OCT with a VCSEL light source at 400kHz sweep rate for phase-sensitive Doppler imaging, measuring pulsatile total retinal blood flow with high sensitivity and phase stability. A robust, simple, and computationally efficient phase stabilization approach for phase-sensitive swept source imaging is also presented. PMID:23381430

  16. Sub-cycle QAM modulation for VCSEL-based optical fiber links.

    PubMed

    Pham, Tien-Thang; Rodes, Roberto; Jensen, Jesper Bevensee; Chang-Hasnain, Connie J; Monroy, Idelfonso Tafur

    2013-01-28

    QAM modulation utilizing subcarrier frequency lower than the symbol rate is both theoretically and experimentally investigated. High spectral efficiency and concentration of power in low frequencies make sub-cycle QAM signals attractive for optical fiber links with direct modulated light sources. Real-time generated 10-Gbps 4-level QAM signal in a 7.5-GHz bandwidth utilizing subcarrier frequency at a half symbol rate was successfully transmitted over 20-km SMF using an un-cooled 1.5-µm VCSEL. Only 2.5-dB fiber transmission power penalty was observed with no equalization applied. PMID:23389167

  17. Polarization control in X-ray FELs by reverse undulator tapering

    NASA Astrophysics Data System (ADS)

    Schneidmiller, E. A.; Yurkov, M. V.

    2015-05-01

    Baseline design of a typical X-ray FEL undulator assumes a planar configuration which results in a linear polarization of the FEL radiation. However, many experiments at X-ray FEL user facilities would profit from using a circularly polarized radiation. As a cheap upgrade one can consider an installation of a short helical (or cross-planar) afterburner, but then one should have an efficient method to suppress powerful linearly polarized background from the main undulator. In this paper we propose a new method for such a suppression: an application of the reverse taper in the main undulator. We discover that in a certain range of the taper strength, the density modulation (bunching) at saturation is practically the same as in the case of non-tapered undulator while the power of linearly polarized radiation is suppressed by orders of magnitude. Then strongly modulated electron beam radiates at full power in the afterburner. Considering SASE3 undulator of the European XFEL as a practical example, we demonstrate that soft X-ray radiation pulses with peak power in excess of 100 GW and an ultimately high degree of circular polarization can be produced. The proposed method is rather universal, i.e. it can be used at SASE FELs and seeded (self-seeded) FELs, with any wavelength of interest, in a wide range of electron beam parameters, and with any repetition rate.

  18. Linearly polarized emission from an embedded quantum dot using nanowire morphology control.

    PubMed

    Foster, Andrew P; Bradley, John P; Gardner, Kirsty; Krysa, Andrey B; Royall, Ben; Skolnick, Maurice S; Wilson, Luke R

    2015-03-11

    GaAs nanowires with elongated cross sections are formed using a catalyst-free growth technique. This is achieved by patterning elongated nanoscale openings within a silicon dioxide growth mask on a (111)B GaAs substrate. It is observed that MOVPE-grown vertical nanowires with cross section elongated in the [21?1?] and [1?12] directions remain faithful to the geometry of the openings. An InGaAs quantum dot with weak radial confinement is realized within each nanowire by briefly introducing indium into the reactor during nanowire growth. Photoluminescence emission from an embedded nanowire quantum dot is strongly linearly polarized (typically >90%) with the polarization direction coincident with the axis of elongation. Linearly polarized PL emission is a result of embedding the quantum dot in an anisotropic nanowire structure that supports a single strongly confined, linearly polarized optical mode. This research provides a route to the bottom-up growth of linearly polarized single photon sources of interest for quantum information applications. PMID:25674919

  19. Scattering Intensity and Directionality Probed Along Individual Zinc Oxide Nanorods with Precisely Controlled Light Polarization and Nanorod Orientation

    PubMed Central

    Choi, Daniel S.; Singh, Manpreet; Song, Sheng; Chang, Jae Young; Kang, Yongkoo; Hahm, Jong-in

    2015-01-01

    We elucidated the light-matter interaction of individual ZnO NRs with a monochromatic beam of linearly polarized light that scatters elastically from the ZnO NRs by performing forward scattering and back-aperture imaging in a dark-field setting. We precisely controlled the electric field vector of the incident light and the NR orientation within the plane of light interaction during both modes of measurement, and spatially resolved the scattering response from different interaction points along the NR long axis. We then discerned, for the first time, the effects of light polarization, analyzer angle, and NR orientation on the intensity and directionality of the optical responses both qualitatively and quantitatively along the length of the single ZnO NRs. We identified distinctive scattering profiles from individual ZnO NRs subject to incident light polarization with controlled NR orientation from the forward dark-field scattering and back-aperture imaging modes. The fundamental light interaction behavior of ZnO NRs is likely to govern their functional outcomes in photonics, optoelectronics, and sensor devices. Hence, our efforts provided much needed insight into unique optical responses from individual 1D ZnO nanomaterials, which could be highly beneficial in developing next-generation optoelectronic systems and optical biodetectors with improved device efficiency and sensitivity. PMID:26568952

  20. The spatio-temporal domains of Frizzled6 action in planar polarity control of hair follicle orientation.

    PubMed

    Chang, Hao; Smallwood, Philip M; Williams, John; Nathans, Jeremy

    2016-01-01

    In mammals, hair follicles cover most of the body surface and exhibit precise and stereotyped orientations relative to the body axes. Follicle orientation is controlled by the planar cell polarity (PCP; or, more generally, tissue polarity) system, as determined by the follicle mis-orientation phenotypes observed in mice with PCP gene mutations. The present study uses conditional knockout alleles of the PCP genes Frizzled6 (Fz6), Vangl1, and Vangl2, together with a series of Cre drivers to interrogate the spatio-temporal domains of PCP gene action in the developing mouse epidermis required for follicle orientation. Fz6 is required starting between embryonic day (E)11.5 and E12.5. Eliminating Fz6 in either the anterior or the posterior halves of the embryo or in either the feet or the torso leads to follicle mis-orientation phenotypes that are limited to the territories associated with Fz6 loss, implying either that PCP signaling is required for communicating polarity information on a local but not a global scale, or that there are multiple independent sources of global polarity information. Eliminating Fz6 in most hair follicle cells or in the inter-follicular epidermis at E15.5 suggests that PCP signaling in developing follicles is not required to maintain their orientation. The asymmetric arrangement of Merkel cells around the base of each guard hair follicle dependents on Fz6 expression in the epidermis but not in differentiating Merkel cells. These experiments constrain current models of PCP signaling and the flow of polarity information in mammalian skin. PMID:26517967

  1. Controlling circular polarization of light emitted by quantum dots using chiral photonic crystal slabs

    NASA Astrophysics Data System (ADS)

    Lobanov, S. V.; Tikhodeev, S. G.; Gippius, N. A.; Maksimov, A. A.; Filatov, E. V.; Tartakovskii, I. I.; Kulakovskii, V. D.; Weiss, T.; Schneider, C.; Geßler, J.; Kamp, M.; Höfling, S.

    2015-11-01

    We study the polarization properties of light emitted by quantum dots that are embedded in chiral photonic crystal structures made of achiral planar GaAs waveguides. A modification of the electromagnetic mode structure due to the chiral grating fabricated by partial etching of the waveguide layer has been shown to result in a high circular polarization degree ?c of the quantum dot emission in the absence of external magnetic field. The physical nature of the phenomenon can be understood in terms of the reciprocity principle taking into account the structural symmetry. At the resonance wavelength, the magnitude of | ?c| is predicted to exceed 98%. The experimentally achieved value of | ?c|=81 % is smaller, which is due to the contribution of unpolarized light scattered by grating defects, thus breaking its periodicity. The achieved polarization degree estimated removing the unpolarized nonresonant background from the emission spectra can be estimated to be as high as 96%, close to the theoretical prediction.

  2. Generation and control of spin-polarized photocurrents in GaMnAs heterostructures

    SciTech Connect

    Bezerra, Anibal T. Farinas, Paulo F.; Studart, Nelson; Degani, Marcos H.; Maialle, Marcelo Z.

    2014-01-13

    Photocurrents are calculated for a specially designed GaMnAs semiconductor heterostructure. The results reveal regions in the infrared range of the energy spectrum, in which the proposed structure is remarkably spin-selective. For such photon energies, the generated photocurrents are strongly spin-polarized. Application of a relatively small static bias in the growth direction of the structure is predicted to efficiently reverse the spin-polarization for some photon energies. This behavior suggests the possibility of conveniently simple switching mechanisms. The physics underlying the results is studied and understood in terms of the spin-dependent properties emerging from the particular potential profile of the structure.

  3. Polarization-controlled contrasted images using dye-doped nematic liquid crystals.

    PubMed

    Porras Aguilar, R; Ramirez-San-Juan, J C; Baldovino-Pantaleon, O; May-Arrioja, D; Arroyo Carrasco, M L; Iturbe-Castillo, M D; Sánchez-de-la-Llave, D; Ramos-Garcia, R

    2009-03-01

    We explore the polarization dependence of the nonlinear response of a planar nematic liquid crystal cell doped with 1% wt of methyl red dye. The results obtained show that the refractive index change can be switched from a positive value to a negative one as the polarization of the beam changes from parallel to perpendicular with respect to the rubbing direction. This property is exploited in a phase contrast system, where a dynamic phase filter is photoinduced in a liquid crystal cell placed in the system's Fourier plane. Real-time contrast inversion in the resulting images is demonstrated. PMID:19259179

  4. A quantum dot single-photon source with on-the-fly all-optical polarization control and timed emission

    NASA Astrophysics Data System (ADS)

    Heinze, Dirk; Breddermann, Dominik; Zrenner, Artur; Schumacher, Stefan

    2015-10-01

    Sources of single photons are key elements for applications in quantum information science. Among the different sources available, semiconductor quantum dots excel with their integrability in semiconductor on-chip solutions and the potential that photon emission can be triggered on demand. Usually, the photon is emitted from a single-exciton ground state. Polarization of the photon and time of emission are either probabilistic or pre-determined by electronic properties of the system. Here, we study the direct two-photon emission from the biexciton. The two-photon emission is enabled by a laser pulse driving the system into a virtual state inside the band gap. From this intermediate state, the single photon of interest is then spontaneously emitted. We show that emission through this higher-order transition provides a versatile approach to generate a single photon. Through the driving laser pulse, polarization state, frequency and emission time of the photon can be controlled on-the-fly.

  5. Route to polarization switching induced by optical injection in vertical-cavity surface-emitting lasers

    SciTech Connect

    Sciamanna, M.; Panajotov, K.

    2006-02-15

    We perform a theoretical investigation of the polarization dynamics in a vertical-cavity surface-emitting laser (VCSEL) subject to orthogonal optical injection, i.e., the injected field has a linear polarization (LP) orthogonal to that of the free-running VCSEL. In agreement with previous experiments [Z. G. Pan et al., Appl. Phys. Lett. 63, 2999 (1993)], an increase of the injection strength may lead to a polarization switching accompanied by an injection locking. We find that this route to polarization switching is typically accompanied by a cascade of bifurcations to wave-mixing dynamics and time-periodic and possibly chaotic regimes. A detailed mapping of the polarization dynamics in the plane of the injection parameters (detuning, injection strength) unveils a large richness of dynamical scenarios. Of particular interest is the existence of another injection-locked solution for which the two LP modes both lock to the master laser frequency, i.e., an elliptically polarized injection-locked (EPIL) steady state. Modern continuation techniques allow us to unveil an unfolding mechanism of the EPIL solution as the detuning varies and also to link the existence of the EPIL solution to a resonance condition between the master laser frequency and the free-running frequency of the normally depressed LP mode in the slave laser. We furthermore report an additional case of bistability, in which the EPIL solution may coexist with the second injection-locked solution (the one being locked to the master polarization). This case of bistability is a result of the interaction between optical injection and the two-polarization-mode characteristics of VCSEL devices.

  6. Collimating diode laser beams from a large-area VCSEL-array using microlens array

    SciTech Connect

    Chen, H.L.; Francis, D.; Nguyen, T.; Yuen, W.; Li, G.; Chang-Hasnain, C.

    1999-05-01

    In this letter, the authors demonstrate the fabrication and bonding of a 1 cm {times} 1 cm monolithic two-dimensional (2-D) vertical-cavity surface-emitting laser (VCSEL) array. They coupled the array to a matched microlens array to individually collimate light from each laser. They found the beam divergence of the collimated array to be 1.6{degree} (1/e{sup 2}) for the entire array. Using a 1-cm diameter F2 lens, they were able to focus the collimated beams to a spot of 400 {micro}m in diameter and to couple more than 75% of the array power into a 1-mm core fiber. The results show that it is possible to uniformly bond large area VCSEL arrays to heat sinks, and to collimate light from each element into parallel beams using a single 2-D microlens array. The results also show that the brightness of the focused beam can be further increased with a lens to near 10{sup 5}-W/cm{sup 2} Steradian, a level that is useful for many high-power applications.

  7. Ultrahigh speed endoscopic optical coherence tomography using micromotor imaging catheter and VCSEL technology.

    PubMed

    Tsai, Tsung-Han; Potsaid, Benjamin; Tao, Yuankai K; Jayaraman, Vijaysekhar; Jiang, James; Heim, Peter J S; Kraus, Martin F; Zhou, Chao; Hornegger, Joachim; Mashimo, Hiroshi; Cable, Alex E; Fujimoto, James G

    2013-07-01

    We developed a micromotor based miniature catheter with an outer diameter of 3.2 mm for ultrahigh speed endoscopic swept source optical coherence tomography (OCT) using a vertical cavity surface-emitting laser (VCSEL) at a 1 MHz axial scan rate. The micromotor can rotate a micro-prism at several hundred frames per second with less than 5 V drive voltage to provide fast and stable scanning, which is not sensitive to the bending of the catheter. The side-viewing probe can be pulled back to acquire a three-dimensional (3D) data set covering a large area on the specimen. The VCSEL provides a high axial scan rate to support dense sampling under high frame rate operation. Using a high speed data acquisition system, in vivo 3D-OCT imaging in the rabbit GI tract and ex vivo imaging of a human colon specimen with 8 ?m axial resolution, 8 ?m lateral resolution and 1.2 mm depth range in tissue at a frame rate of 400 fps was demonstrated. PMID:23847737

  8. InAlGaP vertical cavity surface emitting lasers (VCSELs): Processing and performance

    SciTech Connect

    Crawford, M.H.; Choquette, K.D.; Hickman, R.J.; Geib, K.M.

    1997-06-01

    (Al{sub y}Ga{sub 1{minus}y}){sup 1{minus}x}In{sub x}P semiconductor alloys lattice-matched to GaAs are widely used in visible optoelectronic devices. One of the most recent developments in this area is the AlGaInP-based red vertical cavity surface emitting laser (VCSEL). These lasers, which employ AlGaInP active regions and AlGaAs distributed Bragg reflectors (DBRs), have demonstrated continuous-wave (CW) lasing over the 630--690 nm region of the spectrum. Applications for these lasers include plastic fiber data communications, laser printing and bar code scanning. In this paper, the authors present an overview of recent developments in the processing and performance of AlGaInP based VCSELs. This overview will include a review of the general heterostructure designs that have been employed, as well as the performance of lasers fabricated by both ion implantation and selective oxidation.

  9. Ultrahigh speed endoscopic optical coherence tomography using micromotor imaging catheter and VCSEL technology

    PubMed Central

    Tsai, Tsung-Han; Potsaid, Benjamin; Tao, Yuankai K.; Jayaraman, Vijaysekhar; Jiang, James; Heim, Peter J. S.; Kraus, Martin F.; Zhou, Chao; Hornegger, Joachim; Mashimo, Hiroshi; Cable, Alex E.; Fujimoto, James G.

    2013-01-01

    We developed a micromotor based miniature catheter with an outer diameter of 3.2 mm for ultrahigh speed endoscopic swept source optical coherence tomography (OCT) using a vertical cavity surface-emitting laser (VCSEL) at a 1 MHz axial scan rate. The micromotor can rotate a micro-prism at several hundred frames per second with less than 5 V drive voltage to provide fast and stable scanning, which is not sensitive to the bending of the catheter. The side-viewing probe can be pulled back to acquire a three-dimensional (3D) data set covering a large area on the specimen. The VCSEL provides a high axial scan rate to support dense sampling under high frame rate operation. Using a high speed data acquisition system, in vivo 3D-OCT imaging in the rabbit GI tract and ex vivo imaging of a human colon specimen with 8 ?m axial resolution, 8 ?m lateral resolution and 1.2 mm depth range in tissue at a frame rate of 400 fps was demonstrated. PMID:23847737

  10. Controlled polarization for q-ary alphabets Woomyoung Park Alexander Barg

    E-print Network

    Barg, Alexander

    a new proof of the polarization result of [5]. The results of [3]. Let W : X Y be a discrete memoryless = (v1, v2, . . . , vr) we denote wtHr(v) = max(i : vi = 1) (the location of the rightmost nonzero bit

  11. Controlling the excitation process of free electrons by a femtosecond elliptically polarized laser

    NASA Astrophysics Data System (ADS)

    Gao, Lili; Wang, Feng; Jiang, Lan; Qu, Liangti; Lu, Yongfeng

    2015-11-01

    This paper is focused on the excitation rates of free electrons of an aluminum (Al) bulk irradiated by an elliptically polarized laser in simulation, using time-dependent density functional theory (TDDFT). The polarized 400 nm, 10 fs laser pulse consisted of two elementary sinusoidal beams, and is adjusted by changing the phase difference ? and the intersection angle ? of the polarization directions between the two beams. The simulation includes cases of ? = ?/2 with ? = 30°, ? = 45°, ? = 60°, ? = 90°, ? = 120°, ? = 135°, ? = 150°, and cases of ? = 90° with ? = ?/4, ? = ?/3, ? = ?/2, ? = 2?/3, ? = 3?/4. The absorbed energy, the excitation rates and the density distributions of free electrons after laser termination are investigated. At the given power intensity (1×1014Wcm-2), pulse width (10 fs) and wavelength (400 nm) of each elementary laser beam, computational results indicate that the excitation rate of free electrons is impacted by three major factors: the long axis direction of the laser projected profile, the amplitude difference of the first main oscillation (1st AD), and the total amplitude difference of main oscillations (TAD) of the external electric field. Among the aforementioned three factors for the excitation rate of free electrons, the direction of long axis plays the most significant role. The screen effect is crucial to compare the importance of the remaining two factors. The analysis approach to investigate the electron dynamics under an elliptically polarized laser is both pioneering and effective.

  12. Subnatural-Linewidth Polarization-Entangled Photon Pairs with Controllable Temporal Length

    E-print Network

    Du, Shengwang

    in the past more than one decade ago to narrow down the SPDC photon bandwidth by using optical cavities [3,9]. Our motivation was stimulated by the recent progress in generating subnatural-linewidth biphotons [16]. The "writ- ing-reading" technique with optical pumping provides a solution to polarization

  13. Rictor Regulates Spermatogenesis by Controlling Sertoli Cell Cytoskeletal Organization and Cell Polarity in the Mouse Testis.

    PubMed

    Dong, Heling; Chen, Zhenguo; Wang, Caixia; Xiong, Zhi; Zhao, Wanlu; Jia, Chunhong; Lin, Jun; Lin, Yan; Yuan, Weiping; Zhao, Allan Z; Bai, Xiaochun

    2015-11-01

    Maintenance of cell polarity is essential for Sertoli cell and blood-testis barrier (BTB) function and spermatogenesis; however, the signaling mechanisms that regulate the integrity of the cytoskeleton and polarity of Sertoli cells are not fully understood. Here, we demonstrate that rapamycin-insensitive component of target of rapamycin (TOR) (Rictor), a core component of mechanistic TOR complex 2 (mTORC2), was expressed in the seminiferous epithelium during testicular development, and was down-regulated in a cadmium chloride-induced BTB damage model. We then conditionally deleted the Rictor gene in Sertoli cells and mutant mice exhibited azoospermia and were sterile as early as 3 months old. Further study revealed that Rictor may regulate actin organization via both mTORC2-dependent and mTORC2-independent mechanisms, in which the small GTPase, ras-related C3 botulinum toxin substrate 1, and phosphorylation of the actin filament regulatory protein, Paxillin, are involved, respectively. Loss of Rictor in Sertoli cells perturbed actin dynamics and caused microtubule disarrangement, both of which accumulatively disrupted Sertoli cell polarity and BTB integrity, accompanied by testicular developmental defects, spermiogenic arrest and excessive germ cell loss in mutant mice. Together, these findings establish the importance of Rictor/mTORC2 signaling in Sertoli cell function and spermatogenesis through the maintenance of Sertoli cell cytoskeletal dynamics, BTB integrity, and cell polarity. PMID:26360620

  14. The putative Poc complex controls two distinct Pseudomonas aeruginosa polar motility mechanisms

    PubMed Central

    Cowles, Kimberly N.; Moser, Theresa S.; Siryaporn, Albert; Nyakudarika, Natsai; Dixon, William; Turner, Jonathan J.; Gitai, Zemer

    2015-01-01

    Summary Each Pseudomonas aeruginosa cell localizes two types of motility structures, a single flagellum and one or two clusters of type IV pili, to the cell poles. Previous studies suggested that these motility structures arrive at the pole through distinct mechanisms. Here we performed a swimming motility screen to identify polar flagellum localization factors and discovered three genes homologous to the TonB/ExbB/ExbD complex that have defects in both flagella-mediated swimming and pilus-mediated twitching motility. We found that deletion of tonB3, PA2983 or PA2982 led to non-polar localization of the flagellum and FlhF, which was thought to sit at the top of the flagellar localization hierarchy. Surprisingly, these mutants also exhibited pronounced changes in pilus formation or localization, indicating that these proteins may co-ordinate both the pilus and flagellum motility systems. Thus, we have renamed PA2983 and PA2982, pocA and pocB, respectively, for polar organelle co-ordinator to reflect this function. Our results suggest that TonB3, PocA and PocB may form a membrane-associated complex, which we term the Poc complex. These proteins do not exhibit polar localization themselves, but are required for increased expression of pilus genes upon surface association, indicating that they regulate motility structures through either localization or transcriptional mechanisms. PMID:24102920

  15. Calibrations, noise, and long-term drift characteristics of the HIAPER VCSEL hygrometer

    NASA Astrophysics Data System (ADS)

    Brubaker, K. A.; Paige, M. E.; Silver, J. A.; Zondlo, M. A.

    2006-12-01

    Water vapor plays extremely important roles in the climate, chemistry, and dynamics of the atmosphere. Unfortunately, it is difficult to measure accurately, particularly in the upper troposphere and lower stratosphere. The NSF/NCAR Gulfstream-V HIAPER aircraft can sample in tropical moist air in the marine boundary layer to the very cold and dry air of the stratosphere. We are characterizing, testing, and calibrating a water vapor sensor to fly on HIAPER. The sensor uses a vertical cavity surface emitting laser (VCSEL) operating near 1854 nm, an open path cell with 1.9 cm diameter mirrors separated by 15 cm, and a fiber optic to deliver the infrared light. To accommodate the wide range of concentrations to be measured, the instrument can scan across two different water avpor absorption lines, a weak line at 1853.37 nm for moist air and a strong line at 1854.03 nm for dry air. Measurement specifications include 5 percent accuracy over the range from 1 ppmv at 60 mb to 4 percent mixing ratio at sea level. Initial calibrations of the instrument are being conducted by three methods: 1) comparing it with a chilled mirror hygrometer; 2) a standard dilution system of flows of nitrogen controlled by critical orifices; and 3) placing the instrument inside a vessel saturated with water vapor and immersing it in a constant, cold temperature bath. First results from the laboratory suggest that the HIAPER instrument shows excellent agreement over the chilled mirror hygrometer down to 55 C frost point. The standard dilution system of dry and saturated flows with the critical orifices also yields very good agreement with chilled mirror and HIAPER. A consistent moist offset of about 20 ppmv above the calculated frost points from the standard dilution of flows was observed until the system dried out. We have also conducted Allan variance tests to look at instrument noise and drift on 25 Hz to 2 hour timescales for constant, calibrated flows from 0.81 ppmv to 7640 ppmv. The Allan deviations show that random noise is the dominant source of noise up to ~ 80-100 s. Allan deviations for 1 Hz measurements were below 5 percent of the signal down to ~ 80 ppmv when outgassing became a more important source of noise. Long-term drift remains below the precision of the 25 Hz and 1 Hz data for up to two hours. Noise levels from the instrument are about a factor of two higher than our target specification of a minimum detectable absorbance of 1 x 10-5 at 1 Hz. However, the noise continually improves as the system dries out, and thus we suspect that at least some of this noise is related to water vapor outgassing and unrelated to optical noise from interference fringers. The drift on timescales of 1000 s is related to thermal cycling of the room temperature, and we are currently examining methods to reduce these drifts even further. Methods to truly calibrate at sub-ppmv levels as well as additional results on immersing the optical cell in a saturated, sealed chamber at low frost points (< - 40 C) will also be discussed.

  16. Slmb antagonises the aPKC/Par-6 complex to control oocyte and epithelial polarity

    PubMed Central

    Morais-de-Sá, Eurico; Mukherjee, Avik; Lowe, Nick; St Johnston, Daniel

    2014-01-01

    The Drosophila anterior-posterior axis is specified when the posterior follicle cells signal to polarise the oocyte, leading to the anterior/lateral localisation of the Par-6/aPKC complex and the posterior recruitment of Par-1, which induces a microtubule reorganisation that localises bicoid and oskar mRNAs. Here we show that oocyte polarity requires Slmb, the substrate specificity subunit of the SCF E3 ubiquitin ligase that targets proteins for degradation. The Par-6/aPKC complex is ectopically localised to the posterior of slmb mutant oocytes, and Par-1 and oskar mRNA are mislocalised. Slmb appears to play a related role in epithelial follicle cells, as large slmb mutant clones disrupt epithelial organisation, whereas small clones show an expansion of the apical domain, with increased accumulation of apical polarity factors at the apical cortex. The levels of aPKC and Par-6 are significantly increased in slmb mutants, whereas Baz is slightly reduced. Thus, Slmb may induce the polarisation of the anterior-posterior axis of the oocyte by targeting the Par-6/aPKC complex for degradation at the oocyte posterior. Consistent with this, overexpression of the aPKC antagonist Lgl strongly rescues the polarity defects of slmb mutant germline clones. The role of Slmb in oocyte polarity raises an intriguing parallel with C. elegans axis formation, in which PAR-2 excludes the anterior PAR complex from the posterior cortex to induce polarity, but its function can be substituted by overexpressing Lgl. PMID:25053432

  17. High power 808 nm VCSEL arrays for pumping of compact pulsed high energy Nd:YAG lasers operating at 946 nm and 1064 nm for blue and UV light generation

    NASA Astrophysics Data System (ADS)

    Van Leeuwen, Robert; Xiong, Yihan; Watkins, Laurence S.; Seurin, Jean-Francois; Xu, Guoyang; Wang, Qing; Ghosh, Chuni

    2011-02-01

    High power 808 nm VCSEL arrays were developed to pump compact pulsed Nd:YAG lasers. A QCW side-pumped passively Q-switched Nd:YAG laser operating at 1064 nm produced linearly polarized 4 ns IR pulses with 4.7 mJ pulse energy. These pulses were externally frequency doubled and quadrupled resulting in 2.5 mJ pulse energy at 532 nm and 0.8 mJ at 266 nm respectively. A similar but actively Q-switched dual side-pumped Nd:YAG laser operating at the weaker quasi three-level 946 nm transition produced 12 mJ pulses that were efficiently frequency doubled resulting in 5.6 mJ blue pulses of 17 ns duration.

  18. Ultrafast Laser Beam Switching and Pulse Train Generation by Using Coupled Vertical-Cavity, Surface-Emitting Lasers (VCSELS)

    NASA Technical Reports Server (NTRS)

    Goorjian, Peter M. (Inventor); Ning, Cun-Zheng (Inventor)

    2005-01-01

    Ultrafast directional beam switching is achieved using coupled VCSELs. This approach is demonstrated to achieve beam switching frequencies of 40 GHz and more and switching directions of about eight degrees. This switching scheme is likely to be useful for ultrafast optical networks at frequencies much higher than achievable with other approaches.

  19. A fundamental mode Nd:GdVO4 laser pumped by a large aperture 808 nm VCSEL

    NASA Astrophysics Data System (ADS)

    Hao, Y. Q.; Ma, J. L.; Yan, C. L.; Liu, G. J.; Ma, X. H.; Gong, J. F.; Feng, Y.; Wei, Z. P.; Wang, Y. X.; Zhao, Y. J.

    2013-05-01

    A fundamental mode Nd:GdVO4 laser pumped by a vertical cavity surface emitting laser (VCSEL) is experimentally demonstrated. The VCSEL has a circular output-beam which makes it easier for it to be directly coupled to a Nd:GdVO4 microcrystal. In our research, a large aperture 808 nm VCSEL, with a multi-ring-shaped aperture (MRSA) and an almost Gaussian-shaped far-field profile, is used as the pumping source. Experimental results for the Nd:GdVO4 laser pumped by the VCSEL are presented. The maximum output peak power of 0.754 W is obtained under a pump peak power of 1.3 W, and the corresponding opto-optic conversion efficiency is 58.1%. The average slope efficiency is 65.8% from the threshold pump power of 0.2 W to the pump power of 1.3 W. The laser beam quality factors are measured to be {M}x2=1.2 0 and {M}y2=1.1 5.

  20. JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 21, NO. 6, JUNE 2003 1531 Performance Analysis of 10-m-Thick VCSEL

    E-print Network

    Chen, Ray

    in printed circuit board (PCB) is further analyzed. The experimental results show an excellent matchJOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 21, NO. 6, JUNE 2003 1531 Performance Analysis of 10-m-Thick VCSEL Array in Fully Embedded Board Level Guided-Wave Optoelectronic Interconnects Chulchae Choi, Lei

  1. PLR-1, a putative E3 ubiquitin ligase, controls cell polarity and axonal extensions in C. elegans.

    PubMed

    Bhat, Jaffar M; Pan, Jie; Hutter, Harald

    2015-02-01

    During embryonic development neurons differentiate and extend axons and dendrites that have to reach their appropriate targets. In Caenorhabditis elegans the AVG neuron is the first neuron to extend an axon during the establishment of the ventral nerve cord, the major longitudinal axon tract in the animal. In genetic screens we isolated alleles of plr-1, which caused polarity reversals of the AVG neuron as well as outgrowth and navigation defects of the AVG axon. In addition plr-1 mutants show outgrowth defects in several other classes of neurons as well as the posterior excretory canals. plr-1 is predicted to encode a transmembrane E3 ubiquitin ligase and is widely expressed in the animal including the AVG neuron and the excretory cell. plr-1 has recently been shown to negatively regulate Wnt signalling by removing Wnt receptors from the cell surface. We observed that mutations in a gene reducing Wnt signalling as well as mutations in unc-53/NAV2 and unc-73/Trio suppress the AVG polarity defects in plr-1 mutants, but not the defects seen in other cells. This places plr-1 in a Wnt regulation pathway, but also suggests that plr-1 has Wnt independent functions and interacts with unc-53 and unc-73 to control cell polarity. PMID:25448694

  2. Gate-voltage-controlled spin and valley polarization transport in a normal/ferromagnetic/normal MoS? junction.

    PubMed

    Li, Hai; Shao, Jianmei; Yao, Daoxin; Yang, Guowei

    2014-02-12

    Two-dimensional (2D) materials are extensively explored due to the remarkable physical property and the great potential for post-silicon electronics since the landmark achievement of graphene. The monolayer (ML) MoS2 with a direct energy gap is a typical 2D material and promising candidate for a wide range of device applications. The extensive efforts so far have focused on the optical valley control applications of ML MoS2 rather than the electrical control of spin and valley transport. However, the electrical manipulation of spin injection and transport is essential to realize practical spintronics applications. Here, we theoretically demonstrated that the valley and spin transport can be electrically manipulated by a gate voltage in a normal/ferromagnetic/normal monolayer MoS2 junction device. It was found that the fully valley- and spin-polarized conductance can be achieved due to the spin-valley coupling of valence-band edges together with the exchange field, and both the amplitude and direction of the fully spin-polarized conductance can be modulated by the gate voltage. These findings not only provided deep understanding to the basic physics in the spin and valley transport of ML MoS2 but also opened an avenue for the electrical control of valley and spin transport in monolayer dichalcogenide-based devices. PMID:24417464

  3. Efficiency optimization and analysis of 808nm VCSELs with a full electro-thermal-optical numerical model

    NASA Astrophysics Data System (ADS)

    Engelhardt, Andreas P.; Kolb, Johanna S.; Roemer, Friedhard; Weichmann, Ulrich; Moench, Holger; Witzigmann, Bernd

    2015-03-01

    A high electro-optical conversion efficiency of a VCSEL (Vertical-Cavity Surface-Emitting Lasers) is one of the key requirements for their application in high power systems for heating, illumination and pumping applications. The substantial amount of degrees of freedom in the epitaxial and structural design of a VCSEL demands numerical guidance in form of technology computer aided design (TCAD) modeling for a straight forward and successful optimization of the devices. We set up a full electro-thermal optical model for the simulation of VCSEL devices. The electro-thermal part of the simulation follows a drift-diffusion model complemented by a customized, energy resolved, semi-classical carrier capture theory in the QW regions. Optical modes, eigensolutions of the vectorial electromagnetic wave equation, stem from a finite element vectorial solver. The electro-thermal and optical models are linked via the photon-rate equation using QW gain spectra (screened Hartree-Fock approximation) and iterated to self-consistency in a Gummel-type iteration scheme. For comparison and calibration, experimental reference data was extracted from oxide-confined, top-emitting VCSEL devices with an emission wavelength of 808 nm. Our simulations are in good agreement with the electro-optical characteristics of the experimental reference. With the calibrated, microscopic model, routes of design adjustment for efficiency optimization are explored. Exemplarily, the maximum VCSEL efficiency of the simulated reference design increases by 10% (absolute) when free hole absorption is switched off. Accordingly, with the combination of an electro-thermal and optical description, a balancing of the tradeoffs of pDBR doping towards reduced free carrier absorption results in a noteworthy efficiency improvement which is validated with experimental data.

  4. Specific polar subpopulations of astral microtubules control spindle orientation and symmetric neural stem cell division.

    PubMed

    Mora-Bermúdez, Felipe; Matsuzaki, Fumio; Huttner, Wieland B

    2014-01-01

    Mitotic spindle orientation is crucial for symmetric vs asymmetric cell division and depends on astral microtubules. Here, we show that distinct subpopulations of astral microtubules exist, which have differential functions in regulating spindle orientation and division symmetry. Specifically, in polarized stem cells of developing mouse neocortex, astral microtubules reaching the apical and basal cell cortex, but not those reaching the central cell cortex, are more abundant in symmetrically than asymmetrically dividing cells and reduce spindle orientation variability. This promotes symmetric divisions by maintaining an apico-basal cleavage plane. The greater abundance of apical/basal astrals depends on a higher concentration, at the basal cell cortex, of LGN, a known spindle-cell cortex linker. Furthermore, newly developed specific microtubule perturbations that selectively decrease apical/basal astrals recapitulate the symmetric-to-asymmetric division switch and suffice to increase neurogenesis in vivo. Thus, our study identifies a novel link between cell polarity, astral microtubules, and spindle orientation in morphogenesis. PMID:24996848

  5. Control of Electronic Conduction at an Oxide Heterointerface using Surface Polar Adsorbates

    SciTech Connect

    Bell, Christopher

    2011-08-19

    We study the effect of the surface adsorption of a variety of common laboratory solvents on the conductivity at the interface between LaAlO{sub 3} and SrTiO{sub 3}. This interface possesses a range of intriguing physics, notably a proposed connection between the surface state of the LaAlO{sub 3} and the conductivity buried in the SrTiO{sub 3}. We show that the application of chemicals such as acetone, ethanol, and water can induce a large change (factor of three) in the conductivity. This phenomenon is observed only for polar solvents. These data provide experimental evidence for a general polarization-facilitated electronic transfer mechanism.

  6. Microbial Competition in Polar Soils: A Review of an Understudied but Potentially Important Control on Productivity

    PubMed Central

    Bell, Terrence H.; Callender, Katrina L.; Whyte, Lyle G.; Greer, Charles W.

    2013-01-01

    Intermicrobial competition is known to occur in many natural environments, and can result from direct conflict between organisms, or from differential rates of growth, colonization, and/or nutrient acquisition. It has been difficult to extensively examine intermicrobial competition in situ, but these interactions may play an important role in the regulation of the many biogeochemical processes that are tied to microbial communities in polar soils. A greater understanding of how competition influences productivity will improve projections of gas and nutrient flux as the poles warm, may provide biotechnological opportunities for increasing the degradation of contaminants in polar soil, and will help to predict changes in communities of higher organisms, such as plants. PMID:24832797

  7. Off-resonant polarized light-controlled thermoelectric transport in ultrathin topological insulators

    NASA Astrophysics Data System (ADS)

    Tahir, M.; Vasilopoulos, P.

    2015-03-01

    We study thermoelectric transport in ultrathin topological insulators under the application of circularly polarized off-resonant light of frequency ? and amplitude A . We derive analytical expressions for the band structure, orbital magnetization Morb, and the thermal (?x y) and Nernst (?x y) conductivities. Reversing the light polarization from right to left leads to an exchange of the conduction and valence bands of the symmetric and antisymmetric surface states and to a sign change in Morb,?x y, and ?x y. Varying the sample thickness or A /? leads to a strong enhancement of Morb and ?x y. These effects, accessible to experiments, open the possibility for selective, state-exchanged excitations under light and the conversion of heat to electric energy.

  8. Polarization-resolved cartography of light emission of a vertical-cavity surface-emitting laser with high space and frequency resolution

    NASA Astrophysics Data System (ADS)

    Wang, T.; Lippi, G. L.

    2015-11-01

    We couple a double-channel imaging technique, allowing for the simultaneous acquisition of high-quality and high-resolution intensity and peak emission wavelength profiles [T. Wang and G. L. Lippi, Rev. Sci. Instrum. 86, 063111 (2015)], to the polarization-resolved analysis of the optical emission of a multimode vertical-cavity surface-emitting laser (VCSEL). Detailed information on the local wavelength shifts between the two polarized components and on the wavelength gradients can be easily gathered. A polarization- and position-resolved energy balance can be constructed for each wavelength component, allowing in a simple way for a direct analysis of the collected light. Applications to samples, other than VCSELs, are suggested.

  9. Multiple wavelength vertical-cavity surface-emitting laser arrays using surface-controlled MOCVD growth rate enhancement and reduction

    SciTech Connect

    Ortiz, G.G.; Hains, C.P.; Luong, S.; Cheng, J.; Hou, H.Q.; Vawter, G.A.

    1997-04-01

    Multiple-wavelength VCSEL and photodetector arrays are useful for wavelength-multiplexed fiberoptic networks, and for optical crosstalk isolation in parallel, free-space interconnects. Multiple wavelength VCSEL arrays have been obtained by varying the growth rate using thermal gradients caused by a backside-patterned substrate, by growth enhancement on a patterned substrate, and by varying the cavity length through anodic oxidation and selective etching of the wafer. We show here for the first time both the enhancement and the reduction of the growth rate of the entire VCSEL structure on a topographically patterned substrate, and demonstrate the controlled variation of the lasing wavelengths of a VCSEL array over an extended spectral range.

  10. Robust and tunable 16.375Gb/s dual-band optical OFDM transmissions over directly modulated VCSEL-based 200m OM2 MMFs.

    PubMed

    Deng, M L; Jiang, N; Duan, X; Giddings, R P; Yi, X W; Cao, B Y; Mansoor, S; Qiu, K; Tang, J M

    2015-01-12

    Utilizing low-cost, 2.2GHz modulation bandwidth, uncooled and standalone directly modulated VCSEL (DM-VCSEL)-based real-time dual-band optical OFDM (OOFDM) transmitters, aggregated 16.375Gb/s transmissions of OOFDM signals having bandwidths approximately 3.8 times higher than the VCSEL manufacturer-specified modulation bandwidths, are experimentally demonstrated, for the first time, over 200m OM2 MMF links based on intensity modulation and direct detection. The aggregated signal transmission capacities of the aforementioned links vary by just 8% for various OM2 MMFs ranging from 100m to 500m, and by just 10% over a 1GHz passband carrier frequency detuning range. Such dual-band OOFDM adaptability-induced excellent performance robustness and large passband frequency tunability can significantly relax the requirements on VCSEL modulation bandwidth for achieving specific transmission performances for cost-sensitive application scenarios such as data centers. PMID:25835683

  11. Flat frequency comb generation based on efficiently multiple four-wave mixing without polarization control

    NASA Astrophysics Data System (ADS)

    Dong, Qimeng; Sun, Bao; Chen, Fushen; Jiang, Jun

    2015-09-01

    This paper presents a new technique for flat optical frequency comb (OFC) generation, which is based on the nonlinear process of multiple four-wave mixing (FWM) effects. The nonlinear effects are significantly enhanced by using the proposed optical feedback scheme consisting of a single mode fiber (SMF), two highly nonlinear fibers (HNLFs) with different zero dispersion wavelengths (ZDWs) and polarization beam splitters (PBSs). Simulation results illustrate its efficiency and applicability of expanding a comb to 128 coherent lines spaced by only 20 GHz within 6-dB power deviation.

  12. Controlling spin-polarized electron transport through a molecule: The role of molecular conformation

    NASA Astrophysics Data System (ADS)

    Senapati, L.; Pati, R.; Erwin, S. C.

    2007-07-01

    We investigate theoretically the spin-polarized electron transport through a complex organic molecule coupled to magnetic contacts. Our focus is on how low-energy deformations of the molecule affect the current-voltage characteristics and the magnetotransport of this molecular-scale device. We find that fairly modest deformations, costing only a few tens of meVs, can substantially change the tunneling current—by factors of 2 or more. Such deformations have still larger impact on the magnetoresistance, with small changes in molecular conformation even leading to changes in the sign of the magnetoresistance.

  13. Position- and orientation-controlled polarized light interaction of individual indium tin oxide nanorods

    SciTech Connect

    Choi, Daniel S.; Joh, Daniel Y.; Lee, Thomas; Milchak, Marissa; Zhou, Hebing; Kang, Yongkoo; Hahm, Jong-in

    2014-02-24

    We have systematically investigated the position, orientation, and polarization angle dependence of scattered light from well-characterized, indium tin oxide nanorods (ITO NRs) upon illumination with monochromatic light. Scattering signals from individual ITO NRs of horizontal and vertical configurations are probed quantitatively by examining signal response with respect to the analyzer angle and position along the length of the NR. Our efforts can be highly beneficial in providing fundamental understanding for the light interaction behavior of ITO NRs. Our results can provide valuable bases for comprehending optical emission from individual NRs, with their ever-growing applications in optoelectronics, photonics, and biosensing.

  14. Comprehensive analysis of electrically-pumped GaSb-based VCSELs.

    PubMed

    Arafin, S; Bachmann, A; Vizbaras, K; Hangauer, A; Gustavsson, J; Bengtsson, J; Larsson, A; Amann, M-C

    2011-08-29

    This paper discusses several performance-related aspects of electrically-pumped GaSb-based buried tunnel junction VCSELs with an emission wavelength of 2.6 ?m based on theoretical and experimental results. These results allow a deeper insight into the internal device physics, such as radial diffusion of carriers, maximum continuous-wave operating temperature, diffraction loss, internal temperature, gain and loss parameters, internal quantum efficiency of the active region etc. These parameters can be taken into account while designing mid-infrared lasers which leads to an improved device performance. A simple thermal model of the devices based on the two-dimensional (2-D) finite element method using the material data from the literature is also presented. In addition, an application-based result utilizing these lasers for the measurement of absolute water vapor concentration by wavelength modulation spectroscopy (WMS) method are also described, hinting that devices are well-suited for the targeted sensing applications. PMID:21935091

  15. Optimal oxide-aperture for improving the power conversion efficiency of VCSEL arrays

    NASA Astrophysics Data System (ADS)

    Wang, Wen-Juan; Li, Chong; Zhou, Hong-Yi; Wu, Hua; Luan, Xin-Xin; Shi, Lei; Guo, Xia

    2015-02-01

    The maximum power conversion efficiencies of the top-emitting, oxide-confined, two-dimensional integrated 2×2 and 4×4 vertical-cavity surface-emitting laser (VCSEL) arrays with the oxide-apertures of 6 ?m, 16 ?m, 19 ?m, 26 ?m, 29 ?m, 36 ?m, 39 ?m, and 46 ?m are fabricated and characterized, respectively. The maximum power conversion efficiencies increase rapidly with the augment of oxide-aperture at the beginning and then decrease slowly. A maximum value of 27.91% at an oxide-aperture of 18.6 ?m is achieved by simulation. The experimental data are well consistent with the simulation results, which are analyzed by utilizing an empirical model. Project supported by the National Natural Science Foundation of China (Grant Nos. 61222501 and 61335004) and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20111103110019)

  16. 1060-nm VCSEL-based parallel-optical modules for optical interconnects

    NASA Astrophysics Data System (ADS)

    Nishimura, N.; Nagashima, K.; Kise, T.; Rizky, A. F.; Uemura, T.; Nekado, Y.; Ishikawa, Y.; Nasu, H.

    2015-03-01

    The capability of mounting a parallel-optical module onto a PCB through solder-reflow process contributes to reduce the number of piece parts, simplify its assembly process, and minimize a foot print for both AOC and on-board applications. We introduce solder-reflow-capable parallel-optical modules employing 1060-nm InGaAs/GaAs VCSEL which leads to the advantages of realizing wider modulation bandwidth, longer transmission distance, and higher reliability. We demonstrate 4-channel parallel optical link performance operated at a bit stream of 28 Gb/s 231-1 PRBS for each channel and transmitted through a 50-?m-core MMF beyond 500 m. We also introduce a new mounting technology of paralleloptical module to realize maintaining good coupling and robust electrical connection during solder-reflow process between an optical module and a polymer-waveguide-embedded PCB.

  17. Volumetric cutaneous microangiography of human skin in vivo by VCSEL swept-source optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Choi, Woo June; Wang, R. K.

    2014-08-01

    We demonstrate volumetric cutaneous microangiography of the human skin in vivo that utilises 1.3-?m high-speed sweptsource optical coherence tomography (SS-OCT). The swept source is based on a micro-electro-mechanical (MEMS)-tunable vertical cavity surface emission laser (VCSEL) that is advantageous in terms of long coherence length over 50 mm and 100 nm spectral bandwidth, which enables the visualisation of microstructures within a few mm from the skin surface. We show that the skin microvasculature can be delineated in 3D SS-OCT images using ultrahigh-sensitive optical microangiography (UHS-OMAG) with a correlation mapping mask, providing a contrast enhanced blood perfusion map with capillary flow sensitivity. 3D microangiograms of a healthy human finger are shown with distinct cutaneous vessel architectures from different dermal layers and even within hypodermis. These findings suggest that the OCT microangiography could be a beneficial biomedical assay to assess cutaneous vascular functions in clinic.

  18. Controlled calcite nucleation on polarized calcite single crystal substrates in the presence of polyacrylic acid

    NASA Astrophysics Data System (ADS)

    Wada, Norio; Horiuchi, Naohiro; Nakamura, Miho; Nozaki, Kosuke; Hiyama, Tetsuo; Nagai, Akiko; Yamashita, Kimihiro

    2015-04-01

    We studied theoretically and experimentally the effects of the surface electric field generated by polarization and polyacrylic acid (PAA) additives on the heterogeneous nucleation of calcite on the calcite single crystal substrates with (10.4), (10.0) and (00.1) orientations. A set of "in-situ" experiments with optical microscopy was performed to determine the waiting time of CaCO3 nucleation, defined as the time interval between the onset of the diffusion of CO2 and the appearance of the first visible precipitation. Calcite was nucleated on the oriented calcite substrates through diffusion of NH3 and CO2 gas from a solid ammonium carbonate into calcium chloride solutions. A theoretical analysis showed that the surface electric field of the polarized calcite substrate decrease the activation energy for nucleation and consequently promotes nucleation. Experimentally, the surface electric field and PAA addition were found to decrease both contact angles and waiting times, and as a result, promote the heterogeneous nucleation. Combined effect of PAA and surface electric field further reduced contact angles and waiting times regardless of orientation differences of the calcite substrates. The cooperation acts remarkably on N-surface of the respective calcite substrates. The results were explained by the Cassie's equation, a classical heterogeneous nucleation theory under a surface electric field, and matching of the charged sites on the PAA chain with the ion arrangement on the calcite substrate.

  19. VANGL2 regulates membrane trafficking of MMP14 to control cell polarity and migration.

    PubMed

    Williams, B Blairanne; Cantrell, V Ashley; Mundell, Nathan A; Bennett, Andrea C; Quick, Rachel E; Jessen, Jason R

    2012-05-01

    Planar cell polarity (PCP) describes the polarized orientation of cells within the plane of a tissue. Unlike epithelial PCP, the mechanisms underlying PCP signaling in migrating cells remain undefined. Here, the establishment of PCP must be coordinated with dynamic changes in cell adhesion and extracellular matrix (ECM) organization. During gastrulation, the membrane type-1 matrix metalloproteinase (MT1-MMP or MMP14) is required for PCP and convergence and extension cell movements. We report that the PCP protein Vang-like 2 (VANGL2) regulates the endocytosis and cell-surface availability of MMP14 in manner that is dependent on focal adhesion kinase. We demonstrate that zebrafish trilobite/vangl2 mutant embryos exhibit increased Mmp14 activity and decreased ECM. Furthermore, in vivo knockdown of Mmp14 partially rescues the Vangl2 loss-of-function convergence and extension phenotype. This study identifies a mechanism linking VANGL2 with MMP14 trafficking and suggests that establishment of PCP in migrating gastrula cells requires regulated proteolytic degradation or remodeling of the ECM. Our findings implicate matrix metalloproteinases as downstream effectors of PCP and suggest a broadly applicable mechanism whereby VANGL2 affects diverse morphogenetic processes. PMID:22357946

  20. Controllable fully spin-polarized transport in a ferromagnetically doped topological insulator junction

    SciTech Connect

    Zhou, Benliang; Tang, Dongsheng; Zhou, Guanghui; Zhou, Benhu

    2014-04-21

    We investigate the energy band structure and the spin-dependent transport for a normal/ferromagnetic/normal two-dimension topological insulator (TI) junction. By diagonalizing Hamiltonian for the system, the band structure shows that the edge states on two sides are coupled resulting in a gap opening due to the transverse spatial confinement. Further, the exchange field induced by magnetic impurities can also modulate the band structure with two spin degenerate bands splitting. By using the nonequilibrium Green's function method, the dependence of spin-dependent conductance and spin-polarization on the Fermi energy, the exchange field strength and the ferromagnetic TI (FTI) length are also analyzed, respectively. Interestingly, the degenerate conductance plateaus for spin-up and -down channels are broken, and both the conductances are suppressed by magnetic impurities due to the time-reversal symmetry broken and inelastic scattering. The spin-dependent conductance shows different behaviors when the Fermi energy is tuned into different ranges. Moreover, the conductance can be fully spin polarized by tuning the Fermi energy and the exchange field strength, or by tuning the Fermi energy and the FTI length. Consequently, the junction can transform from a quantum spin Hall state to a quantum anomalous Hall state, which is very important to enable dissipationless charge current for designing perfect spin filter.

  1. Control of vibrational states by spin-polarized transport in a carbon nanotube resonator

    NASA Astrophysics Data System (ADS)

    Stadler, P.; Belzig, W.; Rastelli, G.

    2015-02-01

    We study spin-dependent transport in a suspended carbon nanotube quantum dot in contact with two ferromagnetic leads and with the dot's spin coupled to the flexural mechanical modes. The spin-vibration interaction induces spin-flip processes between the two energy levels of the dot. This interaction arises from the spin-orbit coupling or a magnetic field gradient. The inelastic vibration-assisted spin flips give rise to a mechanical damping and, for an applied bias voltage, to a steady nonequilibrium occupation of the harmonic oscillator. We analyze these effects as function of the energy-level separation of the dot and the magnetic polarization of the leads. Depending on the magnetic configuration and the bias-voltage polarity, we can strongly cool a single mode or pump energy into it. In the latter case, we find that within our approximation, the system approaches eventually a regime of mechanical instability. Furthermore, owing to the sensitivity of the electron transport to the spin orientation, we find signatures of the nanomechanical motion in the current-voltage characteristic. Hence, the vibrational state can be read out in transport measurements.

  2. 850 nm single mode VCSEL-based 25Gx16 transmitter/receiver boards for parallel signal transmission over 1 km of multimode fiber

    NASA Astrophysics Data System (ADS)

    Kropp, J.-R.; Shchukin, V. A.; Ledentsov, N. N.; Schaefer, G.; Ledentsov, N. N.; Wu, Bo; Shaofeng, Qiu; Yanan, Ma; Zhiyong, Feng; Turkiewicz, J. P.

    2015-03-01

    We manufacture and compare parallel optical transceiver and receiver assemblies on test boards for parallel data transmission over multimode fiber using single mode (SM) and multimode (MM) vertical-cavity surface-emitting laser (VCSEL) arrays. VCSELs, GaAs PIN photodetector arrays, commercially-available 12 channel VCSEL driver arrays and 12 channel limiting amplifier arrays were assembled into multi-channel transceiver and receiver assemblies on testboards designed to operate up to 16 channels and coupled to multimode fiber ribbon through industrial connectors. MM VCSEL arrays easily allow 25 Gb/s error-free data transmission over 100m of OM4 fiber with only a minor penalty in the sensitivity (0.5 dB). As opposite increasing the distance to 150-200 m causes a strong increase in the noise level making the error free transmission at 200 m impossible. Using of single mode SM VCSEL arrays allows error-free 25 Gbit/s NRZ PRBS 215-1 transmission over 1 km distances over OM4 fiber and above 600 m over OM3 fiber. In a different set of experiments PAM4 transmission up to 50 Gbit/s using SM VCSEL arrays is studied.

  3. B. Madhavan and A. F. J. Levi: `Low-power 2.5 Gbps VCSEL driver in 0.5 m CMOS technology' page 1 Electronics Letters 34, 178-179 (1998).

    E-print Network

    Levi, Anthony F. J.

    1998-01-01

    B. Madhavan and A. F. J. Levi: `Low-power 2.5 Gbps VCSEL driver in 0.5 µm CMOS technology' page 1 Electronics Letters 34, 178-179 (1998). Low-power 2.5 Gbps VCSEL driver in 0.5 µm CMOS technology Bindu. F. J. Levi: `Low-power 2.5 Gbps VCSEL driver in 0.5 µm CMOS technology' page 2 Electronics Letters

  4. Quasi-continuous metasurface for ultra-broadband and polarization-controlled electromagnetic beam deflection.

    PubMed

    Wang, Yanqin; Pu, Mingbo; Zhang, Zuojun; Li, Xiong; Ma, Xiaoliang; Zhao, Zeyu; Luo, Xiangang

    2015-01-01

    Two-dimensional metasurface has attracted growing interest in recent years, owing to its ability in manipulating the phase, amplitude and polarization state of electromagnetic wave within a single interface. However, most existing metasurfaces rely on the collective responses of a set of discrete meta-atoms to perform various functionalities. In this paper, we presented a quasi-continuous metasurface for high-efficiency and broadband beam steering in the microwave regime. It is demonstrated both in simulation and experiment that the incident beam deviates from the normal direction after transmitting through the ultrathin metasurface. The efficiency of the proposed metasurface approximates to the theoretical limit of the single-layer metasurface in a broad frequency range, owing to the elimination of the circuit resonance in traditional discrete structures. The proposed scheme promises potential applications in broadband electromagnetic modulation and communication systems, etc. PMID:26635228

  5. Quasi-continuous metasurface for ultra-broadband and polarization-controlled electromagnetic beam deflection

    PubMed Central

    Wang, Yanqin; Pu, Mingbo; Zhang, Zuojun; Li, Xiong; Ma, Xiaoliang; Zhao, Zeyu; Luo, Xiangang

    2015-01-01

    Two-dimensional metasurface has attracted growing interest in recent years, owing to its ability in manipulating the phase, amplitude and polarization state of electromagnetic wave within a single interface. However, most existing metasurfaces rely on the collective responses of a set of discrete meta-atoms to perform various functionalities. In this paper, we presented a quasi-continuous metasurface for high-efficiency and broadband beam steering in the microwave regime. It is demonstrated both in simulation and experiment that the incident beam deviates from the normal direction after transmitting through the ultrathin metasurface. The efficiency of the proposed metasurface approximates to the theoretical limit of the single-layer metasurface in a broad frequency range, owing to the elimination of the circuit resonance in traditional discrete structures. The proposed scheme promises potential applications in broadband electromagnetic modulation and communication systems, etc. PMID:26635228

  6. A quantum dot single-photon source with on-the-fly all-optical polarization control and timed emission.

    PubMed

    Heinze, Dirk; Breddermann, Dominik; Zrenner, Artur; Schumacher, Stefan

    2015-01-01

    Sources of single photons are key elements for applications in quantum information science. Among the different sources available, semiconductor quantum dots excel with their integrability in semiconductor on-chip solutions and the potential that photon emission can be triggered on demand. Usually, the photon is emitted from a single-exciton ground state. Polarization of the photon and time of emission are either probabilistic or pre-determined by electronic properties of the system. Here, we study the direct two-photon emission from the biexciton. The two-photon emission is enabled by a laser pulse driving the system into a virtual state inside the band gap. From this intermediate state, the single photon of interest is then spontaneously emitted. We show that emission through this higher-order transition provides a versatile approach to generate a single photon. Through the driving laser pulse, polarization state, frequency and emission time of the photon can be controlled on-the-fly. PMID:26436776

  7. A quantum dot single-photon source with on-the-fly all-optical polarization control and timed emission

    PubMed Central

    Heinze, Dirk; Breddermann, Dominik; Zrenner, Artur; Schumacher, Stefan

    2015-01-01

    Sources of single photons are key elements for applications in quantum information science. Among the different sources available, semiconductor quantum dots excel with their integrability in semiconductor on-chip solutions and the potential that photon emission can be triggered on demand. Usually, the photon is emitted from a single-exciton ground state. Polarization of the photon and time of emission are either probabilistic or pre-determined by electronic properties of the system. Here, we study the direct two-photon emission from the biexciton. The two-photon emission is enabled by a laser pulse driving the system into a virtual state inside the band gap. From this intermediate state, the single photon of interest is then spontaneously emitted. We show that emission through this higher-order transition provides a versatile approach to generate a single photon. Through the driving laser pulse, polarization state, frequency and emission time of the photon can be controlled on-the-fly. PMID:26436776

  8. Ssp1 CaMKK: A Sensor of Actin Polarization That Controls Mitotic Commitment through Srk1 in Schizosaccharomyces pombe

    PubMed Central

    Giménez-Zaragoza, David; López-Avilés, Sandra; Yance-Chávez, Tula; Montserrat, Marta; Pujol, M. Jesús; Bachs, Oriol; Aligue, Rosa

    2015-01-01

    Background Calcium/calmodulin-dependent protein kinase kinase (CaMKK) is required for diverse cellular functions. Mammalian CaMKK activates CaMKs and also the evolutionarily-conserved AMP-activated protein kinase (AMPK). The fission yeast Schizosaccharomyces pombe CaMKK, Ssp1, is required for tolerance to limited glucose through the AMPK, Ssp2, and for the integration of cell growth and division through the SAD kinase Cdr2. Results Here we report that Ssp1 controls the G2/M transition by regulating the activity of the CaMK Srk1. We show that inhibition of Cdc25 by Srk1 is regulated by Ssp1; and also that restoring growth polarity and actin localization of ssp1-deleted cells by removing the actin-monomer-binding protein, twinfilin, is sufficient to suppress the ssp1 phenotype. Conclusions These findings demonstrate that entry into mitosis is mediated by a network of proteins, including the Ssp1 and Srk1 kinases. Ssp1 connects the network of components that ensures proper polarity and cell size with the network of proteins that regulates Cdk1-cyclin B activity, in which Srk1 plays an inhibitory role. PMID:26575035

  9. Controlling helicity-correlated beam asymmetries in a polarized electron source

    SciTech Connect

    Kent Paschke

    2007-07-01

    The control of helicity-correlated changes in the electron beam is a critical issue for the next generation of parity-violating electron scattering measurements. The underlying causes and methods for controlling these changes are reviewed with reference to recent operational experience at Jefferson Lab.

  10. Design of Control Instrumentation of a 4 meter Variable Polarization Undulator (EPU)

    SciTech Connect

    Kulesza, Joe; Deyhim, Alex; Fan Taiching; Chen, Jenny

    2007-01-19

    The design of a high end, very sophisticated controller, that consists of an Allen Bradley ControlLogix PLC with a Kinetix servo controller for a 4.16 m EPU is presented. Four servo motors control the gap - 2 on the upper girder and 2 on the lower girder, and another 4 servos controls the phase - 2 on the upper girder inner and outer and 2 on the lower girder, inner and outer. This system is designed for The Taiwan Light Source (TLS) a synchrotron radiation machine of the National Synchrotron Radiation Research Center (NSRRC) at the energy of 1.5 GeV with electron beam current of 200 {approx} 400 mA.

  11. Fabrication and performance of 1.3-?m 10-Gb/s CWDM wafer-fused VCSELs grown by MOVPE

    NASA Astrophysics Data System (ADS)

    Mereuta, A.; Sirbu, A.; Caliman, A.; Suruceanu, G.; Iakovlev, V.; Mickovic, Z.; Kapon, E.

    2015-03-01

    Recent progress in the fabrication and performance of 1.3-?m 10-Gb/s, low power consumption wafer-fused VCSELs grown by MOVPE under nitrogen atmosphere are presented and discussed. By optimization of the growth conditions and implementation of a cavity adjustment technique, the wavelength yield was increased to up to 70% for all four coarse wavelength division multiplexing (CWDM) channels implemented. It was demonstrated that single-mode devices can have threshold and operation currents below 1 and 7 mA, respectively, in the full 0-80 °C temperature range. The reproducibility of the fabrication process and prospects for enhancing performance and yield of such VCSELs are also discussed.

  12. A full-duplex lightwave transmission system with an innovative VCSEL-based PM-to-IM converter.

    PubMed

    Lin, Chun-Yu; Lu, Hai-Han; Chang, Ching-Hung; Li, Chung-Yi; Jhang, Tai-Wei; Ruan, Sheng-Siang; Wu, Kuan-Hung

    2014-04-21

    A full-duplex lightwave transmission system employing innovative VCSEL-based PM-to-IM converters to deliver intensity-modulated CATV/phase-modulated RoF/intensity-remodulated RoF signals over two 40-km SMFs links is proposed and demonstrated. To be the first one of employing VCSEL-based PM-to-IM converters in full-duplex lightwave transmission systems, the downstream light is successfully intensity-remodulated with RoF signal for up-link transmission. Good performances of CNR/CSO/CTB are achieved for downstream CATV signal transmission, and low BER values are obtained for both downstream and upstream RoF signals transmissions. Our proposed systems present brilliant performances in delivering hybrid CATV and RoF signals. Such a full-duplex lightwave transmission system would be very attractive for fiber trunk applications to provide broadband integrated services. PMID:24787881

  13. VCSEL-based, high-speed, in situ TDLAS for in-cylinder water vapor measurements in IC engines.

    PubMed

    Witzel, O; Klein, A; Meffert, C; Wagner, S; Kaiser, S; Schulz, C; Ebert, V

    2013-08-26

    We report the first application of a vertical-cavity surfaceemitting laser (VCSEL) for calibration- and sampling-free, high-speed, in situ H2O concentration measurements in IC engines using direct TDLAS (tunable diode laser absorption spectroscopy). Measurements were performed in a single-cylinder research engine operated under motored conditions with a time resolution down to 100 ?s (i.e., 1.2 crank angle degrees at 2000 rpm). Signal-to-noise ratios (1?) up to 29 were achieved, corresponding to a H2O precision of 0.046 vol.% H2O or 39 ppm · m. The modulation frequency dependence of the performance was investigated at different engine operating points in order to quantify the advantages of VCSEL against DFB lasers. PMID:24105541

  14. Integration of GaAs-based VCSEL array on SiN platform with HCG reflectors for WDM applications

    NASA Astrophysics Data System (ADS)

    Kumari, Sulakshna; Gustavsson, Johan S.; Wang, Ruijun; Haglund, Emanuel P.; Westbergh, Petter; Sanchez, Dorian; Haglund, Erik; Haglund, Åsa; Bengtsson, Jörgen; Le Thomas, Nicolas; Roelkens, Gunther; Larsson, Anders; Baets, Roel

    2015-02-01

    We present a GaAs-based VCSEL structure, BCB bonded to a Si3N4 waveguide circuit, where one DBR is substituted by a free-standing Si3N4 high-contrast-grating (HCG) reflector realized in the Si3N4 waveguide layer. This design enables solutions for on-chip spectroscopic sensing, and the dense integration of 850-nm WDM data communication transmitters where individual channel wavelengths are set by varying the HCG parameters. RCWA shows that a 300nm-thick Si3N4 HCG with 800nm period and 40% duty cycle reflects strongly (<99%) over a 75nm wavelength range around 850nm. A design with a standing-optical-field minimum at the III-V/airgap interface maximizes the HCG's influence on the VCSEL wavelength, allowing for a 15-nm-wide wavelength setting range with low threshold gain (<1000 cm-1).

  15. Highly birefringent silicate glass photonic-crystal fiber with polarization-controlled frequency-shifted output: A promising fiber light source for nonlinear Raman microspectroscopy.

    PubMed

    Mitrofanov, Aleksandr V; Linik, Yaroslav M; Buczynski, Ryszard; Pysz, Dariusz; Lorenc, Dusan; Bugar, Ignac; Ivanov, Anatoly A; Alfimov, Mikhail V; Fedotov, Andrei B; Zheltikov, Aleksei M

    2006-10-30

    A highly birefringent silicate glass photonic-crystal fiber (PCF) is employed for polarization-controlled nonlinear-optical frequency conversion of femtosecond Cr: forsterite laser pulses with a central wavelength of 1.24 mum to the 530--720-nm wavelength range through soliton dispersion-wave emission. The fiber exhibits a modal birefringence of 1.2.10(-3) at the wavelength of 1.24 mum due to a strong form anisotropy of its core, allowing polarization switching of the central wavelength of its blue-shifted output by 75 nm. Polarization properties and the beam quality of the blue-shifted PCF output are shown to be ideally suited for polarization-sensitive nonlinear Raman microspectroscopy. PMID:19529469

  16. Electric- and exchange-field controlled transport through silicene barriers: Conductance gap and near-perfect spin polarization

    SciTech Connect

    Vargiamidis, V.; Vasilopoulos, P.

    2014-12-01

    We study ballistic electron transport through silicene barriers, of width d and height U, in the presence of an exchange field M and a normal electric field E{sub z}. Away from the Dirac point (DP), the spin- and valley-resolved conductances, as functions of U, exhibit resonances while close to it there is a pronounced dip that can be transformed into a transport gap by varying E{sub z}. The charge conductance g{sub c} changes from oscillatory to a monotonically decreasing function of d beyond a critical E{sub z} and this can be used to realize electric-field-controlled switching. Further, the field M splits each resonance of g{sub c} into two spin-resolved peaks. The spin polarization near the DP increases with E{sub z} or M and becomes nearly perfect above certain of their values. Similar results hold for double barriers.

  17. Studies of VCSEL Failures in the Optical Readout Systems of the ATLAS Silicon Trackers and Liquid Argon Calorimeters

    E-print Network

    Cooke, Mark S

    2011-01-01

    The readout systems for the ATLAS silicon trackers and liquid argon calorimeters utilize vertical-cavity surface-emitting laser diodes to communicate between on and off detector readout components. A number of these VCSEL devices have failed well before their expected lifetime. We summarize the failure history and present what has been learned thus far about failure mechanisms and the dependence of the lifetime on environmental conditions.

  18. Studies of VCSEL Failures in the Optical Readout Systems of the ATLAS Silicon Trackers and Liquid Argon Calorimeters

    E-print Network

    Mark S. Cooke

    2011-09-29

    The readout systems for the ATLAS silicon trackers and liquid argon calorimeters utilize vertical-cavity surface-emitting laser diodes to communicate between on and off detector readout components. A number of these VCSEL devices have failed well before their expected lifetime. We summarize the failure history and present what has been learned thus far about failure mechanisms and the dependence of the lifetime on environmental conditions.

  19. 1.55-?m optically pumped tunable VCSEL based on a nano-polymer dispersive liquid crystal phase modulator

    NASA Astrophysics Data System (ADS)

    Levallois, C.; Verbrugge, V.; Dupont, L.; de Bougrenet de la Tocnaye, J.-L.; Caillaud, B.; Le Corre, A.; Dehaese, O.; Folliot, H.; Loualiche, S.

    2006-04-01

    We present a new approach to achieve tunability on a 1.55 ?m vertical cavity surface emitting laser (VCSEL). Tunability is achieved thanks to an electro-optic index modulator. This electro-optic material consists in a n-PDLC phase layer introduced inside the VCSEL cavity. N-PDLC comprises nematic liquid crystal dispersed in a polymer material. This first VCSEL exhibits a 10 nm tuning range and an excellent side-mode suppression ratio higher than 20 dB over the whole spectral range. The device is formed by a conventional InP-based active region with an epitaxial and a dielectric Bragg mirror. The n-PDLC layer length, close to 6 ?m, is in agreement with a tunable laser emission without mode-hopping. Another decisive advantage, compared to mechanical solutions, is the tuning response time which is close to a few 10 ?s to scan the full spectral range, making this device appropriate for some access network functions. Voltage values are the main limiting factor, 170 Volts have been required to obtain 10 nm tunability, but material engineering is in progress to improve this point. We presented a first version of the device optically pumped, the next version will be electrically pumped as required for access network applications targeted here.

  20. Inducible Costimulator Protein (Icos) Controls T Helper Cell Subset Polarization after Virus and Parasite Infection

    PubMed Central

    Kopf, Manfred; Coyle, Anthony J.; Schmitz, Nicole; Barner, Marijke; Oxenius, Annette; Gallimore, Awen; Gutierrez-Ramos, Jose-Carlos; Bachmann, Martin F.

    2000-01-01

    It has been shown that certain pathogens can trigger efficient T cell responses in the absence of CD28, a key costimulatory receptor expressed on resting T cells. Inducible costimulator protein (ICOS) is an inducible costimulator structurally and functionally related to CD28. Here, we show that in the absence of CD28 both T helper cell type 1 (Th1) and Th2 responses were impaired but not abrogated after infection with lymphocytic choriomeningitis virus (LCMV), vesicular stomatitis virus (VSV), and the nematode Nippostrongylus brasiliensis. Inhibition of ICOS in CD28-deficient mice further reduced Th1/Th2 polarization. Blocking of ICOS alone had a limited but significant capacity to downregulate Th subset development. In contrast, cytotoxic T lymphocyte (CTL) responses, which are regulated to a minor and major extent by CD28 after LCMV and VSV infection, respectively, remained unaffected by blocking ICOS. Together, our results demonstrate that ICOS regulates both CD28-dependent and CD28-independent CD4+ subset (Th1 and Th2) responses but not CTL responses in vivo. PMID:10880526

  1. Theory and characterization of elliptically polarized modes in vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Volet, Nicolas

    2015-03-01

    The polarization of the beam emitted from telecom-wavelength vertical-cavity surface-emitting lasers (VCSELs) is studied in detail. Stokes parameters are extracted separately for the two polarization submodes of the fundamental spatial mode LP01. This characterization was performed at room temperature and for a significant number of devices. This led to the discovery of stable optical modes with a polarization that differs from the linear case. This crucial result was obtained without immersing the devices in an external magnetic field or driving them under external optical injection. In addition, the polarization can be tuned directly with the drive current. Moreover, the polarization handedness can be switched electrically. A theoretical investigation shows that some of the equations forming the basis of the spin-flip model should be reconsidered. In particular, a generalization of this theory is discussed and fantastic agreement is found with the experimental results. This work paves the way for a broad range of novel applications with the VCSEL technology, in particular for spintronics, bio-chemical sensing and telecommunication.

  2. 1550 nm VCSEL-based 0.48 Tb/s transmission scheme employing PAM-4 and WDM for active optical cables

    NASA Astrophysics Data System (ADS)

    Markou, S.; Dris, S.; Kalavrouziotis, D.; Avramopoulos, H.; Pleros, N.; Tsiokos, Dimitris M.

    2014-05-01

    With this paper we investigate the system-level performance of VCSELs, parameterized with true experimental LI-VI data and dynamic characteristics of state-of-the-art VCSELs with 3 dB modulation bandwidth at 15 GHz, and propose their deployment as high-speed multi-level optical sources in a mid-range active optical cable (AOC) model for performance prediction of a rack-to-rack interconnection. The AOC architecture combines a 6-element 1550 nm VCSEL array, each directly modulated with 40 Gbaud PAM-4 data, with a wavelength division multiplexer (WDM), in order to implement a parallel link with aggregate traffic of 0.48 Tb/s. Transmission reach exceeded 300 m by deploying a two-tap feed forward equalizer filter at the electrical VCSEL driver. Bit Error Rate (BER) measurements and analysis were carried out in MATLAB. In practice, the thermal behavior and basic operational characteristics of the VCSELs fabricated by the Technische Universität München (TUM) were used to study the thermal performance and operational range of the complete AOC model. The VCSELs were initially operated at 20°C and BER measurements showed power penalties of 1.7 dB and 3.5 dB at 300 m and 500 m of transmission distance respectively for all 6 data channels. System performance was also investigated for elevated operating temperatures of the VCSEL module and the additional system degradation and BER penalties introduced by operation at 50°C and 65°C were also investigated for transmission distances of 300 m and 500 m.

  3. Polarization-Controlled TIRFM with Focal Drift and Spatial Field Intensity Correction

    PubMed Central

    Johnson, Daniel S.; Toledo-Crow, Ricardo; Mattheyses, Alexa L.; Simon, Sanford M.

    2014-01-01

    Total internal reflection fluorescence microscopy (TIRFM) is becoming an increasingly common methodology to narrow the illumination excitation thickness to study cellular process such as exocytosis, endocytosis, and membrane dynamics. It is also frequently used as a method to improve signal/noise in other techniques such as in vitro single-molecule imaging, stochastic optical reconstruction microscopy/photoactivated localization microscopy imaging, and fluorescence resonance energy transfer imaging. The unique illumination geometry of TIRFM also enables a distinct method to create an excitation field for selectively exciting fluorophores that are aligned either parallel or perpendicular to the optical axis. This selectivity has been used to study orientation of cell membranes and cellular proteins. Unfortunately, the coherent nature of laser light, the typical excitation source in TIRFM, often creates spatial interference fringes across the illuminated area. These fringes are particularly problematic when imaging large cellular areas or when accurate quantification is necessary. Methods have been developed to minimize these fringes by modulating the TIRFM field during a frame capture period; however, these approaches eliminate the possibility to simultaneously excite with a specific polarization. A new, to our knowledge, technique is presented, which compensates for spatial fringes while simultaneously permitting rapid image acquisition of both parallel and perpendicular excitation directions in ?25 ms. In addition, a back reflection detection scheme was developed that enables quick and accurate alignment of the excitation laser. The detector also facilitates focus drift compensation, a common problem in TIRFM due to the narrow excitation depth, particularly when imaging over long time courses or when using a perfusion flow chamber. The capabilities of this instrument were demonstrated by imaging membrane orientation using DiO on live cells and on lipid bilayers that were supported on a glass slide (supported lipid bilayer). The use of the approach to biological problems was illustrated by examining the temporal and spatial dynamics of exocytic vesicles. PMID:24606926

  4. Polarization feedback laser stabilization

    DOEpatents

    Esherick, P.; Owyoung, A.

    1987-09-28

    A system for locking two Nd:YAG laser oscillators includes an optical path for feeding the output of one laser into the other with different polarizations. Elliptical polarization is incorporated into the optical path so that the change in polarization that occurs when the frequencies coincide may be detected to provide a feedback signal to control one laser relative to the other. 4 figs.

  5. Characterizing and understanding VCSEL polarization noise M.P. van Exter, M.B. Willemsen, and J.P. Woerdman

    E-print Network

    Exter, Martin van

    j 2 \\Gamma jE y j 2 )=I = cos (2Ã?) cos (2OE) Ã? 1 \\Gamma 2(Ã? 2 + OE 2 ) ; (1a) s 2 = \\Gamma2Re(E \\Lambda x E y )=I = cos (2Ã?) sin (2OE) Ã? 2OE ; (1b) s 3 = \\Gamma2I m(E \\Lambda x E y )=I = sin (2Ã?) Ã? 2Ã?. The electric field vector is ~ E = E x ~e x +E y ~e y = p Ie \\Gammai' l [(cos Ã? cos OE \\Gamma i sin Ã? sin OE

  6. Extraction and analysis of high-frequency response and impedance of 980-nm VCSELs as a function of temperature and oxide aperture diameter

    NASA Astrophysics Data System (ADS)

    Wolf, Philip; Li, Hui; Moser, Philip; Larisch, Gunter; Lott, James A.; Bimberg, Dieter

    2015-03-01

    Vertical-cavity surface-emitting lasers (VCSELs) are decisive cost-effective, energy-efficient, and reliable light sources for short-reach (up to ~300 m) optical interconnects in data centers and supercomputers. To viably replace copper interconnects and advance to on-chip integrated photonics, reliable VCSELs ideally must be able to operate highly energy efficient, but at large bit rates and without cooling up to 85 °C, with immunity to temperature variations. Our 980 nm VCSELs achieve such temperature-stable, energy-efficient, and high-speed operation coincidently. Record low 139 fJ/bit of dissipated heat for 35 Gbit/s error-free data transmission at 85 °C is reported. Careful design of both the VCSEL's epitaxial structure and device geometry is of essence. Introducing a suitable gain-to-etalon wavelength offset simultaneously improves the temperature-stability, the maximum bit rate at high temperatures, and the energy efficiency. Tuning the photon lifetime additionally increases the bandwidth by changing the relation between damping and resonance relaxation frequency. Systematic temperature-dependent and oxide aperture-diameter-dependent measurements, including static L-I-V curves and emission spectra, small signal analysis, and data transmission experiments are reported. The modulation bandwidth, the parasitic cut-off frequency, the relaxation resonance frequency, lumped-circuit elements, and the K- and D-factors are derived, useful for energy-efficient optical interconnects based on 980 nm VCSELs.

  7. Stern, C.D. (1987) Control of epithelial polarity and induction in the early chick embryo. In: Mesenchymal-epithelial interactions in neural development (J.R. Wolff, J. Sievers and M.

    E-print Network

    Stern, Claudio

    1987-01-01

    Stern, C.D. (1987) Control of epithelial polarity and induction in the early chick embryo. In and induction in the early chick embryo. In: Mesenchymal-epithelial interactions in neural development (J;Stern, C.D. (1987) Control of epithelial polarity and induction in the early chick embryo. In

  8. Vanin-1 controls granuloma formation and macrophage polarization in Coxiella burnetii infection.

    PubMed

    Meghari, Soraya; Berruyer, Carole; Lepidi, Hubert; Galland, Franck; Naquet, Philippe; Mege, Jean-Louis

    2007-01-01

    Q fever is caused by Coxiella burnetii, a bacterium that survives in MPhi. Vanin-1 is a membrane-anchored pantetheinase that controls tissue inflammation. Consequently, Vanin-1-deficient mice represent a unique mouse model in which stress-induced inflammation is limited by the reaction of resident tissue cells. To investigate the contribution of host tissues in the control of a bacterial infection, we infected Vanin-1-deficient mice with C. burnetii. Mortality and morbidity of mice were not affected. The lack of Vanin-1 had no effect on C. burnetii clearance but decreased the formation of granulomas in spleen and liver. Granuloma formation depends upon MPhi recruitment and activation in these tissues. Whereas the former was slightly impaired in mutant mice, the lack of Vanin-1 significantly affected the activation pattern of BM-derived MPhi stimulated by C. burnetii. While their microbicidal activity against C. burnetii was moderately impaired, they exhibited decreased inducible nitric oxide synthase (iNOS) and MCP-1 gene expression, and increased IL-10 and arginase expression. In liver from mutant mice, increased arginase expression and decreased expression of MCP-1 and iNOS were reminiscent of MPhi data. These results suggest a role of Vanin-1 in granuloma formation in response to C. burnetii by skewing MPhi activation toward an M2 program. PMID:17163446

  9. Effects of Lateral Plasma Density and Temperature Diffusion on VCSEL Performance

    NASA Technical Reports Server (NTRS)

    Li, Jian-Zhong; Cheung, Samson H.; Ning, Cun-Zheng; Biegel, Bryan A. (Technical Monitor)

    2002-01-01

    The hydrodynamic model is further verified by applying to a gain-guided single mode VCSEL. DC effects of D(sub NN): (1) increase threshold current J(sub th) and decrease slope efficiency; (2) within the studied range (50% pumping within threshold and realistic diffusion coefficient for a single mode), the L-I relation scales with the relative Injection current (J/J(sub th) - 1). AC effects of D(sub NN): (1) decrease spectral bandwidth and responsivity of direct-current modulation; (2) within the studied range, the frequency response follows the same formal dependence as predicted without diffusion and under a linear gain model, while the resonant frequency position similarly scales with the relative injection current; (3) therefore, it is concluded that the AC effects of D(sub NN) is purely of static nature and reflected via its influence on ot and J(sub th). Within this study, the nonlinear effects of D(sub NN) are mostly reproducible with an equivalent constant diffusion coefficient.

  10. Optical coupling structure made by imprinting between single-mode polymer waveguide and embedded VCSEL

    NASA Astrophysics Data System (ADS)

    Karppinen, Mikko; Salminen, Noora; Korhonen, Tia; Alajoki, Teemu; Petäjä, Jarno; Bosman, Erwin; Van Steenberge, Geert; Justice, John; Khan, Umar; Corbett, Brian; Boersma, Arjen

    2015-03-01

    Polymer-based integrated optics is attractive for inter-chip optical interconnection applications, for instance, for coupling photonic devices to fibers in high density packaging. In such a hybrid integration scheme, a key challenge is to achieve efficient optical coupling between the photonic chips and waveguides. With the single-mode polymer waveguides, the alignment tolerances become especially critical as compared to the typical accuracies of the patterning processes. We study novel techniques for such coupling requirements. In this paper, we present a waveguide-embedded micro-mirror structure, which can be aligned with high precision, even active alignment method is possible. The structure enables 90 degree bend coupling between a single-mode waveguide and a vertical-emitting/detecting chip, such as, a VCSEL or photodiode, which is embedded under the waveguide layer. Both the mirror structure and low-loss polymer waveguides are fabricated in a process based mainly on the direct-pattern UV nanoimprinting technology and on the use of UVcurable polymeric materials. Fabrication results of the coupling structure with waveguides are presented, and the critical alignment tolerances and manufacturability issues are discussed.

  11. Swept source optical coherence microscopy using a 1310 nm VCSEL light source.

    PubMed

    Ahsen, Osman O; Tao, Yuankai K; Potsaid, Benjamin M; Sheikine, Yuri; Jiang, James; Grulkowski, Ireneusz; Tsai, Tsung-Han; Jayaraman, Vijaysekhar; Kraus, Martin F; Connolly, James L; Hornegger, Joachim; Cable, Alex; Fujimoto, James G

    2013-07-29

    We demonstrate high speed, swept source optical coherence microscopy (OCM) using a MEMS tunable vertical cavity surface-emitting laser (VCSEL) light source. The light source had a sweep rate of 280 kHz, providing a bidirectional axial scan rate of 560 kHz. The sweep bandwidth was 117 nm centered at 1310 nm, corresponding to an axial resolution of 13.1 µm in air, corresponding to 8.1 µm (9.6 µm spectrally shaped) in tissue. Dispersion mismatch from different objectives was compensated numerically, enabling magnification and field of view to be easily changed. OCM images were acquired with transverse resolutions between 0.86 µm - 3.42 µm using interchangeable 40X, 20X and 10X objectives with ~600 µm x 600 µm, ~1 mm x 1 mm and ~2 mm x 2 mm field-of-view (FOV), respectively. Parasitic variations in path length with beam scanning were corrected numerically. These features enable swept source OCM to be integrated with a wide range of existing scanning microscopes. Large FOV mosaics were generated by serially acquiring adjacent overlapping microscopic fields and combining them in post-processing. Fresh human colon, thyroid and kidney specimens were imaged ex vivo and compared to matching histology sections, demonstrating the ability of OCM to image tissue specimens. PMID:23938673

  12. Influence of base-region thickness on the performance of Pnp transistor-VCSEL.

    PubMed

    Nadeem Akram, M; Xiang, Y; Yu, X; Zabel, Thomas; Hammar, Mattias

    2014-11-01

    We have recently reported a 980nm GaAs-based three terminal Pnp transistor-vertical-cavity surface-emitting laser (TVCSEL) operating at room temperature with optical power up to 1.8mW. However, the current gain ? = ?Ic/?Ib was near zero just before lasing and became negative after the lasing threshold. The main cause of the negative current gain was found to be a gradual and position-dependent forward-biasing (saturation) of the base-collector junction with increasing bias even before lasing threshold. In this article, detailed multi-physics device simulations are performed to better understand the device physics, and find ways to avoid the premature saturation of the base-collector junction. We have optimized the thickness of the base region as well as its doping concentration and the location of the quantum wells to ensure that the T-VCSEL is in the active mode throughout its range of operation. That is, the emitter-base junction is forward biased and base-collector junction is reversed biased for sweeping the excess charges out of the base region. PMID:25401889

  13. Swept source optical coherence microscopy using a 1310 nm VCSEL light source

    PubMed Central

    Ahsen, Osman O.; Tao, Yuankai K.; Potsaid, Benjamin M.; Sheikine, Yuri; Jiang, James; Grulkowski, Ireneusz; Tsai, Tsung-Han; Jayaraman, Vijaysekhar; Kraus, Martin F.; Connolly, James L.; Hornegger, Joachim; Cable, Alex; Fujimoto, James G.

    2013-01-01

    We demonstrate high speed, swept source optical coherence microscopy (OCM) using a MEMS tunable vertical cavity surface-emitting laser (VCSEL) light source. The light source had a sweep rate of 280 kHz, providing a bidirectional axial scan rate of 560 kHz. The sweep bandwidth was 117 nm centered at 1310 nm, corresponding to an axial resolution of 13.1 µm in air, corresponding to 8.1 µm (9.6 µm spectrally shaped) in tissue. Dispersion mismatch from different objectives was compensated numerically, enabling magnification and field of view to be easily changed. OCM images were acquired with transverse resolutions between 0.86 µm - 3.42 µm using interchangeable 40X, 20X and 10X objectives with ~600 µm x 600 µm, ~1 mm x 1 mm and ~2 mm x 2 mm field-of-view (FOV), respectively. Parasitic variations in path length with beam scanning were corrected numerically. These features enable swept source OCM to be integrated with a wide range of existing scanning microscopes. Large FOV mosaics were generated by serially acquiring adjacent overlapping microscopic fields and combining them in post-processing. Fresh human colon, thyroid and kidney specimens were imaged ex vivo and compared to matching histology sections, demonstrating the ability of OCM to image tissue specimens. PMID:23938673

  14. Volumetric cutaneous microangiography of human skin in vivo by VCSEL swept-source optical coherence tomography

    PubMed Central

    Choi, Woo June; Wang, Ruikang K.

    2015-01-01

    Three-dimensional (3D) assessment of cutaneous microcirculation in human skin is essential in the identification of disease states in skin or other organs. Few 3D imaging techniques have revealed the skin micro-vasculatures non-invasively and with sufficient imaging depth. Here, we demonstrate volumetric cutaneous microangiography of the human skin in vivo that utilizes a 1.3 µm high-speed swept-source optical coherence tomography (SS-OCT). The swept source is based on a MEMS tunable vertical cavity surface emission laser (VCSEL) that is advantageous in terms of long coherence length over 50 mm and 100 nm spectral bandwidth that enables the visualization of microstructures within a few mm from the skin surface. We show that skin microvasculature can be delineated in 3D SS-OCT images using ultrahigh-sensitive optical microangiography (UHS-OMAG) with a correlation mapping mask, providing a contrast enhanced blood perfusion map with capillary flow sensitivity. 3D microangiograms of a healthy human finger are shown with distinct cutaneous vessel architectures from different dermal layers and even within hypodermis. These findings suggest that the OCT microangiography could be a beneficial biomedical assay to assess cutaneous vascular functions in clinic. PMID:25635163

  15. Ultrahigh speed endoscopic swept source optical coherence tomography using a VCSEL light source and micromotor catheter

    NASA Astrophysics Data System (ADS)

    Tsai, Tsung-Han; Ahsen, Osman O.; Lee, Hsiang-Chieh; Liang, Kaicheng; Giacomelli, Michael G.; Potsaid, Benjamin M.; Tao, Yuankai K.; Jayaraman, Vijaysekhar; Kraus, Martin F.; Hornegger, Joachim; Figueiredo, Marisa; Huang, Qin; Mashimo, Hiroshi; Cable, Alex E.; Fujimoto, James G.

    2014-03-01

    We developed an ultrahigh speed endoscopic swept source optical coherence tomography (OCT) system for clinical gastroenterology using a vertical-cavity surface-emitting laser (VCSEL) and micromotor based imaging catheter, which provided an imaging speed of 600 kHz axial scan rate and 8 ?m axial resolution in tissue. The micromotor catheter was 3.2 mm in diameter and could be introduced through the 3.7 mm accessory port of an endoscope. Imaging was performed at 400 frames per second with an 8 ?m spot size using a pullback to generate volumetric data over 16 mm with a pixel spacing of 5 ?m in the longitudinal direction. Three-dimensional OCT (3D-OCT) imaging was performed in patients with a cross section of pathologies undergoing standard upper and lower endoscopy at the Veterans Affairs Boston Healthcare System (VABHS). Patients with Barrett's esophagus, dysplasia, and inflammatory bowel disease were imaged. The use of distally actuated imaging catheters allowed OCT imaging with more flexibility such as volumetric imaging in the terminal ileum and the assessment of the hiatal hernia using retroflex imaging. The high rotational stability of the micromotor enabled 3D volumetric imaging with micron scale volumetric accuracy for both en face and cross-sectional imaging. The ability to perform 3D OCT imaging in the GI tract with microscopic accuracy should enable a wide range of studies to investigate the ability of OCT to detect pathology as well as assess treatment response.

  16. Volumetric cutaneous microangiography of human skin in vivo by VCSEL swept-source optical coherence tomography

    SciTech Connect

    Woo June Choi; Wang, R K

    2014-08-31

    We demonstrate volumetric cutaneous microangiography of the human skin in vivo that utilises 1.3-?m high-speed sweptsource optical coherence tomography (SS-OCT). The swept source is based on a micro-electro-mechanical (MEMS)-tunable vertical cavity surface emission laser (VCSEL) that is advantageous in terms of long coherence length over 50 mm and 100 nm spectral bandwidth, which enables the visualisation of microstructures within a few mm from the skin surface. We show that the skin microvasculature can be delineated in 3D SS-OCT images using ultrahigh-sensitive optical microangiography (UHS-OMAG) with a correlation mapping mask, providing a contrast enhanced blood perfusion map with capillary flow sensitivity. 3D microangiograms of a healthy human finger are shown with distinct cutaneous vessel architectures from different dermal layers and even within hypodermis. These findings suggest that the OCT microangiography could be a beneficial biomedical assay to assess cutaneous vascular functions in clinic. (laser biophotonics)

  17. Effects of maneuver dynamics on drag polars of the X-29A forward-swept-wing aircraft with automatic wing camber control

    NASA Technical Reports Server (NTRS)

    Hicks, John W.; Moulton, Bryan J.

    1988-01-01

    The camber control loop of the X-29A FSW aircraft was designed to furnish the optimum L/D for trimmed, stabilized flight. A marked difference was noted between automatic wing camber control loop behavior in dynamic maneuvers and in stabilized flight conditions, which in turn affected subsonic aerodynamic performance. The degree of drag level increase was a direct function of maneuver rate. Attention is given to the aircraft flight drag polar effects of maneuver dynamics in light of wing camber control loop schedule. The effect of changing camber scheduling to better track the optimum automatic camber control L/D schedule is discussed.

  18. 10 Gb/s Radiation-Hard VCSEL Array Driver K.K. Gan, P. Buchholz, S. Heidbrink, H. Kagan, R. Kass, J. Moore, D.S. Smith, M. Vogt, M. Ziolkowski

    E-print Network

    Gan, K. K.

    10 Gb/s Radiation-Hard VCSEL Array Driver K.K. Gan, P. Buchholz, S. Heidbrink, H. Kagan, R. Kass, J that contains a 12-channel VCSEL (Vertical Cavity Surface Emitting Laser) array driver operating at 10 Gb/s per channel, yielding an aggregated bandwidth of 120 Gb/s. The design of the 10 Gb/s array driver ASIC

  19. The Importance of Age Control in Defining Apparent Polar Wander Paths of Fast Moving Plates: The Jurassic Case Study

    NASA Astrophysics Data System (ADS)

    Muttoni, G.

    2014-12-01

    During periods of fast plate motion (e.g. Cambrian, Jurassic), plate velocities in excess of ~20 cm/yr (200 km/Myr) relative to the Earth's spin axis have been suggested. Pinning down the position of fast moving plates requires paleomagnetic poles (paleopoles) with age resolution of a few million years. Modern generations of apparent polar wander paths (APWPs) are becoming increasingly sophisticated in handling ever-growing volumes of data, usually by applying moving windows (e.g., 10 Myr) to the available paleopoles. Averaging paleopoles of fast moving plates may however result in loss of resolution whereby abrupt (but real) changes in APWP may appear subdued when a multimillion-year moving window is applied. Episodes of fast motion are better captured by using paleopoles with best age resolution (coupled with good structural control and provided with inclination flattening estimates) grouped within discrete and independent time windows. Best age control is attained when paleopoles are retrieved from laterally reproducible magnetostratigraphic sections calibrated with biostratigraphy and/or radiometric dating and correlated with reference timescales. This approach was recently applied to the construction of the Adria-Africa APWP (Muttoni et al. 2013). Paleopoles from parautochthonous regions of Adria and obtained either from biostratigraphically dated sedimentary rocks, corrected for inclination shallowing, or from radiometrically dated igneous rocks that are regarded as free from inclination shallowing, were compared with coeval, and inclination flattening-free, paleopoles from stable Africa. The resulting composite APWP shows a remarkable agreement with the Kent and Irving (2010) APWP, and displays a rapid polar shift of ~40° during the Jurassic that other APWPs tend to underestimate. This Jurassic monster shift is also predicted for Eurasia. Paleomagnetic data from the Kimmeridgian-Tithonian Garedu Formation of Iran, which was part of Eurasia since the Triassic, indicate a paleolatitude of deposition that is in excellent agreement with the latitude drop predicted by the monster shift (Mattei et al. 2014), which stands as a major and generalized plate motion event of vast and as yet unexplored paleogeographic implications.

  20. Quality Control and Calibration of the Dual-Polarization Radar at Kwajalein, RMI

    NASA Technical Reports Server (NTRS)

    Marks, David A.; Wolff, David B.; Carey, Lawrence D.; Tokay, Ali

    2010-01-01

    Weather radars, recording information about precipitation around the globe, will soon be significantly upgraded. Most of today s weather radars transmit and receive microwave energy with horizontal orientation only, but upgraded systems have the capability to send and receive both horizontally and vertically oriented waves. These enhanced "dual-polarimetric" (DP) radars peer into precipitation and provide information on the size, shape, phase (liquid / frozen), and concentration of the falling particles (termed hydrometeors). This information is valuable for improved rain rate estimates, and for providing data on the release and absorption of heat in the atmosphere from condensation and evaporation (phase changes). The heating profiles in the atmosphere influence global circulation, and are a vital component in studies of Earth s changing climate. However, to provide the most accurate interpretation of radar data, the radar must be properly calibrated and data must be quality controlled (cleaned) to remove non-precipitation artifacts; both of which are challenging tasks for today s weather radar. The DP capability maximizes performance of these procedures using properties of the observed precipitation. In a notable paper published in 2005, scientists from the Cooperative Institute for Mesoscale Meteorological Studies (CIMMS) at the University of Oklahoma developed a method to calibrate radars using statistically averaged DP measurements within light rain. An additional publication by one of the same scientists at the National Severe Storms Laboratory (NSSL) in Norman, Oklahoma introduced several techniques to perform quality control of radar data using DP measurements. Following their lead, the Topical Rainfall Measuring Mission (TRMM) Satellite Validation Office at NASA s Goddard Space Flight Center has fine-tuned these methods for specific application to the weather radar at Kwajalein Island in the Republic of the Marshall Islands, approximately 2100 miles southwest of Hawaii and 1400 miles east of Guam in the tropical North Pacific Ocean. This tropical oceanic location is important because the majority of rain, and therefore the majority of atmospheric heating, occurs in the tropics where limited ground-based radar data are available.

  1. Origin of the Magnetoresistance in Oxide Tunnel Junctions Determined through Electric Polarization Control of the Interface

    NASA Astrophysics Data System (ADS)

    Inoue, Hisashi; Swartz, Adrian G.; Harmon, Nicholas J.; Tachikawa, Takashi; Hikita, Yasuyuki; Flatté, Michael E.; Hwang, Harold Y.

    2015-10-01

    The observed magnetoresistance (MR) in three-terminal (3T) ferromagnet-nonmagnet (FM-NM) tunnel junctions has historically been assigned to ensemble dephasing (Hanle effect) of a spin accumulation, thus offering a powerful approach for characterizing the spin lifetime of candidate materials for spintronics applications. However, due to crucial discrepancies of the extracted spin parameters with known materials properties, this interpretation has come under intense scrutiny. By employing epitaxial artificial dipoles as the tunnel barrier in oxide heterostructures, the band alignments between the FM and NM channels can be controllably engineered, providing an experimental platform for testing the predictions of the various spin accumulation models. Using this approach, we have been able to definitively rule out spin accumulation as the origin of the 3T MR. Instead, we assign the origin of the magnetoresistance to spin-dependent hopping through defect states in the barrier, a fundamental phenomenon seen across diverse systems. A theoretical framework is developed that can account for the signal amplitude, linewidth, and anisotropy.

  2. Controlling the polarity of metalorganic vapor phase epitaxy-grown GaP on Si(111) for subsequent III-V nanowire growth

    NASA Astrophysics Data System (ADS)

    Paszuk, A.; Brückner, S.; Steidl, M.; Zhao, W.; Dobrich, A.; Supplie, O.; Kleinschmidt, P.; Prost, W.; Hannappel, T.

    2015-06-01

    Nanowire growth on heteroepitaxial GaP/Si(111) by metalorganic vapor phase epitaxy requires the [-1-1-1] face, i.e., GaP(111) material with B-type polarity. Low-energy electron diffraction (LEED) allows us to identify the polarity of GaP grown on Si(111), since (2×2) and (1×1) surface reconstructions are associated with GaP(111)A and GaP(111)B, respectively. In dependence on the pre-growth treatment of the Si(111) substrates, we were able to control the polarity of the GaP buffers. GaP films grown on the H-terminated Si(111) surface exhibited A-type polarity, while GaP grown on Si surfaces terminated with arsenic exhibited a (1×1) LEED pattern, indicating B-type polarity. We obtained vertical GaAs nanowire growth on heteroepitaxial GaP with (1×1) surface reconstruction only, in agreement with growth experiments on homoepitaxially grown GaP(111).

  3. High-contrast coherent population trapping based on crossed polarizers method.

    PubMed

    Yano, Yuichiro; Goka, Shigeyoshi

    2014-12-01

    A method based on crossed polarizers to observe high-contrast coherent population trapping (CPT) resonance has been developed. Because crossed polarizers have a simple optical system, our method is suitable for chip-scale atomic clocks (CSACs). In CPT, the Faraday rotation in a linearly polarized light field (lin||lin) was calculated using two pairs of ?-system models; the spectrum of the Faraday rotation is also estimated. After measuring the contrast and linewidth with the crossed-polarizer method, a comparison of the theoretical model and experimental data showed they were in good agreement. Moreover, the experimental results showed that a high contrast (88.4%) and narrow linewidth (1.15 kHz) resonance could be observed using a Cs gas cell and D1-line verticalcavity surface-emitting laser (VCSEL). PMID:25474771

  4. Spin-glass behaviors in carrier polarity controlled Fe3-xTixO4 semiconductor thin films

    NASA Astrophysics Data System (ADS)

    Yamahara, H.; Seki, M.; Adachi, M.; Takahashi, M.; Nasu, H.; Horiba, K.; Kumigashira, H.; Tabata, H.

    2015-08-01

    Carrier-type control of spin-glass (cluster spin-glass) is studied in order to engineer basic magnetic semiconductor elements using the memory functions of spin-glass. A key of carrier-polarity control in magnetite is the valence engineering between Fe(II) and Fe(III) that is achieved by Ti(IV) substitution. Single phases of (001)-oriented Fe3-xTixO4 thin films have been obtained on spinel MgAl2O4 substrates by pulsed laser deposition. Thermoelectric power measurements reveal that Ti-rich films (x = 0.8) show p-type conduction, while Ti-poor films (x = 0.6-0.75) show n-type conduction. The systematic Fe(III) reduction to Fe(II) followed by Ti(IV) substitution in the octahedral sublattice is confirmed by the X-ray absorption spectra. All of the Fe3-xTixO4 films (x = 0.6-0.8) exhibit ferrimagnetism above room temperature. Next, the spin-glass behaviors of Ti-rich Fe2.2Ti0.8O4 film are studied, since this magnetically diluted system is expected to exhibit the spin-glass behaviors. The DC magnetization and AC susceptibility measurements for the Ti-rich Fe2.2Ti0.8O4 film reveal the presence of the spin glass phase. Thermal- and magnetic-field-history memory effects are observed and are attributed to the long time-decay nature of remanent magnetization. The detailed analysis of the time-dependent thermoremanent magnetization reveals the presence of the cluster spin glass state.

  5. Simultaneous control of growth mode and ferromagnetic ordering in Co-doped ZnO layers with Zn polarity

    NASA Astrophysics Data System (ADS)

    Matsui, Hiroaki; Tabata, Hitoshi

    2007-01-01

    In this paper, we describe a new growth technique realizing the simultaneous control of growth mode and ferromagnetic ordering in Co-doped ZnO layers. Remarkable changes in growth occurred as a result of doping with Co ions. Exposure to O2 plasma to generate an oxygen-rich atmosphere was indispensable for the fabrication of undoped ZnO layers given stabilization of the negatively charged growing surface in a two-dimensional (2D) mode. In contrast, the 2D mode of Zn0.94Co0.06O layers was adequately retained in the absence of a plasma source, and was attributable to the covalence provided by the 3d character of Co ions compared with the 4s character of Zn ions. Spontaneous magnetization of Zn0.94Co0.06O layers was closely correlated with the number of free electrons, which was controlled by the activation energy of donor levels. This was also confirmed for O-polar Zn0.94Co0.06O layers. Ferromagnetic (FM) ordering was observed at ne values close to the Mott transition and led to hopping conduction between shallow donor bands. However, levels of p(O2) below 10-6mbar that yielded FM ordering generated a pitted surface and led to crystalline deterioration. Given our understanding of the formation mechanism of pits, we applied a periodic oxygen pressure-modulated epitaxy that resulted in the coherent growth of Co-doped ZnO layers with a 2D mode. This specific growth was effective in producing pit-free surface uniformities over large areas that maintained FM ordering.

  6. The ecological controls on the prevalence of candidate division TM7 in polar regions

    PubMed Central

    Winsley, Tristrom J.; Snape, Ian; McKinlay, John; Stark, Jonny; van Dorst, Josie M.; Ji, Mukan; Ferrari, Belinda C.; Siciliano, Steven D.

    2014-01-01

    The candidate division TM7 is ubiquitous and yet uncultured phylum of the Bacteria that encompasses a commonly environmental associated clade, TM7-1, and a “host-associated” clade, TM7-3. However, as members of the TM7 phylum have not been cultured, little is known about what differs between these two clades. We hypothesized that these clades would have different environmental niches. To test this, we used a large-scale global soil dataset, encompassing 223 soil samples, their environmental parameters and associated bacterial 16S rRNA gene sequence data. We correlated chemical, physical and biological parameters of each soil with the relative abundance of the two major classes of the phylum to deduce factors that influence the groups' seemingly ubiquitous nature. The two classes of the phylum (TM7-1 and TM7-3) were indeed distinct from each other in their habitat requirements. A key determinant of each class' prevalence appears to be the pH of the soil. The class TM7-1 displays a facultative anaerobic nature with correlations to more acidic soils with total iron, silicon, titanium and copper indicating a potential for siderophore production. However, the TM7-3 class shows a more classical oligotrophic, heterotroph nature with a preference for more alkaline soils, and a probable pathogenic role with correlations to extractable iron, sodium and phosphate. In addition, the TM7-3 was abundant in diesel contaminated soils highlighting a resilient nature along with a possible carbon source. In addition to this both classes had unique co-occurrence relationships with other bacterial phyla. In particular, both groups had opposing correlations to the Gemmatimonadetes phylum, with the TM7-3 class seemingly being outcompeted by this phylum to result in a negative correlation. These ecological controls allow the characteristics of a TM7 phylum preferred niche to be defined and give insight into possible avenues for cultivation of this previously uncultured group. PMID:25076941

  7. The ecological controls on the prevalence of candidate division TM7 in polar regions.

    PubMed

    Winsley, Tristrom J; Snape, Ian; McKinlay, John; Stark, Jonny; van Dorst, Josie M; Ji, Mukan; Ferrari, Belinda C; Siciliano, Steven D

    2014-01-01

    The candidate division TM7 is ubiquitous and yet uncultured phylum of the Bacteria that encompasses a commonly environmental associated clade, TM7-1, and a "host-associated" clade, TM7-3. However, as members of the TM7 phylum have not been cultured, little is known about what differs between these two clades. We hypothesized that these clades would have different environmental niches. To test this, we used a large-scale global soil dataset, encompassing 223 soil samples, their environmental parameters and associated bacterial 16S rRNA gene sequence data. We correlated chemical, physical and biological parameters of each soil with the relative abundance of the two major classes of the phylum to deduce factors that influence the groups' seemingly ubiquitous nature. The two classes of the phylum (TM7-1 and TM7-3) were indeed distinct from each other in their habitat requirements. A key determinant of each class' prevalence appears to be the pH of the soil. The class TM7-1 displays a facultative anaerobic nature with correlations to more acidic soils with total iron, silicon, titanium and copper indicating a potential for siderophore production. However, the TM7-3 class shows a more classical oligotrophic, heterotroph nature with a preference for more alkaline soils, and a probable pathogenic role with correlations to extractable iron, sodium and phosphate. In addition, the TM7-3 was abundant in diesel contaminated soils highlighting a resilient nature along with a possible carbon source. In addition to this both classes had unique co-occurrence relationships with other bacterial phyla. In particular, both groups had opposing correlations to the Gemmatimonadetes phylum, with the TM7-3 class seemingly being outcompeted by this phylum to result in a negative correlation. These ecological controls allow the characteristics of a TM7 phylum preferred niche to be defined and give insight into possible avenues for cultivation of this previously uncultured group. PMID:25076941

  8. Robust Design by Antioptimization for Parameter Tolerant GaAs/AlOx High Contrast Grating Mirror for VCSEL Application

    E-print Network

    Chevallier, Christyves; Fressengeas, Nicolas; Jacquet, Joel

    2013-01-01

    A GaAs/AlOx high contrast grating structure design which exhibits a 99.5% high reflectivity for a 425nm large bandwidth is reported. The high contrast grating (HCG) structure has been designed in order to enhance the properties of mid-infrared VCSEL devices by replacing the top Bragg mirror of the cavity. A robust optimization algorithm has been implemented to design the HCG structure not only as an efficient mirror but also as a robust structure against the imperfections of fabrication. The design method presented here can be easily adapted for other HCG applications at different wavelengths.

  9. Performance analysis of communication links based on VCSEL and silicon photonics technology for high-capacity data-intensive scenario.

    PubMed

    Boletti, A; Boffi, P; Martelli, P; Ferrario, M; Martinelli, M

    2015-01-26

    To face the increased demand for bandwidth, cost-effectiveness and simplicity of future Ethernet data communications, a comparison between two different solutions based on directly-modulated VCSEL sources and Silicon Photonics technologies is carried out. Also by exploiting 4-PAM modulation, the transmission of 50-Gb/s and beyond capacity per channel is analyzed by means of BER performance. Applications for optical backplane, very short reach and in case of client-optics networks and intra and inter massive data centers communications (up to 10 km) are taken into account. A comparative analysis based on the power consumption is also proposed. PMID:25835935

  10. Tuning etch selectivity of fused silica irradiated by femtosecond laser pulses by controlling polarization of the writing pulses

    SciTech Connect

    Yu Xiaoming; Zeng Bin; Liao Yang; He Fei; Cheng Ya; Xu Zhizhan; Sugioka, Koji; Midorikawa, Katsumi

    2011-03-01

    We report on experimental study on chemical etch selectivity of fused silica irradiated by femtosecond laser with either linear or circular polarization in a wide range of pulse energies. The relationships between the etch rates and pulse energies are obtained for different polarization states, which can be divided into three different regions. A drop of the etch rate for high pulse energy region is observed and the underlying mechanism is discussed. The advantage of using circularly polarized laser is justified owing to its unique capability of providing a 3D isotropic etch rate.

  11. Spin-based scheme for implementing an N-qubit tunable controlled phase gate in quantum dots by interference of polarized photons

    NASA Astrophysics Data System (ADS)

    Cui, Wen-Xue; Hu, Shi; Guo, Qi; Wang, Hong-Fu; Zhang, Shou

    2014-04-01

    We present a scheme for direct implementation of an N-qubit tunable controlled phase gate for spin qubits in quantum dots coupled to optical cavities, resorting to spin selective dipole coupling interaction and linear optical manipulation. In the scheme, we first design a quantum entangler device to transform the operated physical qubits, which are represented by the states of the electron spins, into non-maximal hybrid entangled states with a certain probability of success via the introduction of auxiliary circularly polarized photons. Then we show that, based on this quantum entangler operation, a spin-based N-qubit tunable controlled phase gate can be probabilistically achieved by the interference and coincidence detection of polarized photons. This might lead to a useful step toward the construction of more efficient quantum circuits and quantum algorithms in solid-state qubits.

  12. Phosphatidylinositol 4,5-Bisphosphate Influences PIN Polarization by Controlling Clathrin-Mediated Membrane Trafficking in Arabidopsis[C][W

    PubMed Central

    Ischebeck, Till; Werner, Stephanie; Krishnamoorthy, Praveen; Lerche, Jennifer; Meijón, Mónica; Stenzel, Irene; Löfke, Christian; Wiessner, Theresa; Im, Yang Ju; Perera, Imara Y.; Iven, Tim; Feussner, Ivo; Busch, Wolfgang; Boss, Wendy F.; Teichmann, Thomas; Hause, Bettina; Persson, Staffan; Heilmann, Ingo

    2013-01-01

    The functions of the minor phospholipid phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P2] during vegetative plant growth remain obscure. Here, we targeted two related phosphatidylinositol 4-phosphate 5-kinases (PI4P 5-kinases) PIP5K1 and PIP5K2, which are expressed ubiquitously in Arabidopsis thaliana. A pip5k1 pip5k2 double mutant with reduced PtdIns(4,5)P2 levels showed dwarf stature and phenotypes suggesting defects in auxin distribution. The roots of the pip5k1 pip5k2 double mutant had normal auxin levels but reduced auxin transport and altered distribution. Fluorescence-tagged auxin efflux carriers PIN-FORMED (PIN1)–green fluorescent protein (GFP) and PIN2-GFP displayed abnormal, partially apolar distribution. Furthermore, fewer brefeldin A–induced endosomal bodies decorated by PIN1-GFP or PIN2-GFP formed in pip5k1 pip5k2 mutants. Inducible overexpressor lines for PIP5K1 or PIP5K2 also exhibited phenotypes indicating misregulation of auxin-dependent processes, and immunolocalization showed reduced membrane association of PIN1 and PIN2. PIN cycling and polarization require clathrin-mediated endocytosis and labeled clathrin light chain also displayed altered localization patterns in the pip5k1 pip5k2 double mutant, consistent with a role for PtdIns(4,5)P2 in the regulation of clathrin-mediated endocytosis. Further biochemical tests on subcellular fractions enriched for clathrin-coated vesicles (CCVs) indicated that pip5k1 and pip5k2 mutants have reduced CCV-associated PI4P 5-kinase activity. Together, the data indicate an important role for PtdIns(4,5)P2 in the control of clathrin dynamics and in auxin distribution in Arabidopsis. PMID:24326589

  13. Strongly Correlated 2D Quantum Phases with Cold Polar Molecules: Controlling the Shape of the Interaction Potential

    SciTech Connect

    Buechler, H. P.; Micheli, A.; Pupillo, G.; Zoller, P.; Demler, E.; Lukin, M.; Prokof'ev, N.

    2007-02-09

    We discuss techniques to tune and shape the long-range part of the interaction potentials in quantum gases of bosonic polar molecules by dressing rotational excitations with static and microwave fields. This provides a novel tool towards engineering strongly correlated quantum phases in combination with low-dimensional trapping geometries. As an illustration, we discuss the 2D superfluid-crystal quantum phase transition for polar molecules interacting via an electric-field-induced dipole-dipole potential.

  14. Applying the data fusion method to evaluation of the performance of two control signals in monitoring polarization mode dispersion effects in fiber optic links

    NASA Astrophysics Data System (ADS)

    Dashtbani Moghari, M.; Rezaei, P.; Habibalahi, A.

    2015-02-01

    With increasing distance and bit rate in fiber optic links the effects of polarization mode dispersion (PMD) have been highlighted. Since PMD has a statistical nature, using a control signal that can provide accurate information to dynamically tune a PMD compensator is of great importance. In this paper, we apply the data fusion method with the aim of introducing a method that can be used to evaluate more accurately the performance of control signals before applying them in a PMD compensation system. Firstly, the minimum and average degree of polarization (DOP_min and DOP_ave respectively) as control signals in monitoring differential group delay (DGD) for a system including all-order PMD are calculated. Then, features including the amounts of sensitivity and ambiguity in DGD monitoring are calculated for NRZ data format as DGD to bit time (DGD/T) varies. It is shown that each of the control signals mentioned has both positive and negative features for efficient DGD monitoring. Therefore, in order to evaluate features concurrently and increase reliability, we employ data fusion to fuse features of each control signal, which makes evaluating and predicting the performance of control signals possible, before applying them in a real PMD compensation system. Finally, the reliability of the results obtained from data fusion is tested in a typical PMD compensator.

  15. Highly efficient active optical interconnect incorporating a partially chlorinated ribbon POF in conjunction with a visible VCSEL.

    PubMed

    Lee, Hak-Soon; Lee, Sang-Shin; Kim, Bong-Seok; Son, Yung-Sung

    2014-05-19

    A low-loss 4-ch active optical interconnect (AOI) enabling passive alignment was proposed and built resorting to a transmitter (Tx) incorporating a red 680-nm VCSEL, which is linked to a receiver (Rx) module via a partially chlorinated ribbon POF. The POF was observed to exhibit an extremely low loss of ~0.24 dB/m at ? = 680 nm, in comparison to ~1.29 dB/m at ? = 850 nm, and a large numerical aperture of ~0.42. Both the Tx and Rx, which taps into a beam router based on collimated beam optics involving a pair of spherical lenses, were meant to be substantially alignment tolerant and compact. The achieved tolerance for the constructed modules was beyond 40 ?m in terms of the positioning of VCSEL and photodetector. The proposed AOI was completed by linking the Tx with the Rx via a 3-m long ribbon POF, incurring a transmission loss of as small as 3.2 dB. The AOI was practically assessed in terms of a high-speed data transmission over a wide range of temperatures and then exploited to convey full HD video signals. PMID:24921299

  16. Analysis of structurally sensitive loss in GaN-based VCSEL cavities and its effect on modal discrimination.

    PubMed

    Hashemi, Ehsan; Bengtsson, Jörgen; Gustavsson, Johan; Stattin, Martin; Cosendey, Gatien; Grandjean, Nicolas; Haglund, Asa

    2014-01-13

    Lateral loss causes optical energy to leave the laser cavity in the transverse, lateral, direction, and is sometimes neglected to simplify the numerical simulations. However, in contrast to outcoupling and absorption losses, we show that the lateral loss can change drastically with only nanometer-sized changes of the cavity structure, from being virtually zero to becoming the major source of cavity loss, since the cavity becomes antiguiding. This can be explained as the opening of a channel of efficient resonant lateral leakage of optical power at a certain oblique propagation angle. A number of different realizations of current apertures and top mirror designs in GaN-based VCSEL cavities, which have been suggested for realization of microcavity lasers emitting in the blue wavelength range, are simulated. Many of these are shown to lead to unintentional antiguiding, which can more than double the threshold gain for lasing. Notably, for strong enough antiguiding the resonant lateral leakage decreases so that the threshold gain values might again be tolerable. This regime has been suggested for robust single-mode operation since earlier predictions, building on analogies with slab waveguides, hinted at a very strong suppression of higher order modes. However, our simulations indicate that for the VCSEL cavities the derived formulas grossly overestimate the modal discrimination. PMID:24515001

  17. Polarization control of an infrared silicon light-emitting diode by dressed photons and analyses of the spatial distribution of doped boron atoms

    NASA Astrophysics Data System (ADS)

    Kawazoe, Tadashi; Nishioka, Katsuhiro; Ohtsu, Motoichi

    2015-06-01

    This paper reports the fabrication of a polarization-controlled infrared LED fabricated by dressed-photon-phonon (DPP)-assisted annealing of a bulk Si crystal. For the DPP-assisted annealing, linearly polarized infrared light with a wavelength of 1.342 ?m was made normally incident on the top surface of the crystal. The photon energy at the peak of the emitted light spectrum of the fabricated LED was close to that of the light irradiated during the DPP-assisted annealing. A degree of polarization of as large as 0.07 was obtained. The spatial distribution of the doped B atoms in the fabricated LED was measured, and the following findings were obtained: (1) B atoms formed pairs in which the separation between the two B atoms was three times the lattice constant of the Si crystal; and (2) the B atom pairs were apt to orient along the direction perpendicular to the propagation direction and to the polarization direction of the light irradiated during the DPP-assisted annealing. Based on these findings (1) and (2), photon breeding was confirmed with respect to photon energy and spin, respectively.

  18. aPKC Phosphorylates p27Xic1, Providing a Mechanistic Link between Apicobasal Polarity and Cell-Cycle Control

    PubMed Central

    Sabherwal, Nitin; Thuret, Raphael; Lea, Robert; Stanley, Peter; Papalopulu, Nancy

    2014-01-01

    Summary During the development of the nervous system, apicobasally polarized stem cells are characterized by a shorter cell cycle than nonpolar progenitors, leading to a lower differentiation potential of these cells. However, how polarization might be directly linked to the kinetics of the cell cycle is not understood. Here, we report that apicobasally polarized neuroepithelial cells in Xenopus laevis have a shorter cell cycle than nonpolar progenitors, consistent with mammalian systems. We show that the apically localized serine/threonine kinase aPKC directly phosphorylates an N-terminal site of the cell-cycle inhibitor p27Xic1 and reduces its ability to inhibit the cyclin-dependent kinase 2 (Cdk2), leading to shortening of G1 and S phases. Overexpression of activated aPKC blocks the neuronal differentiation-promoting activity of p27Xic1. These findings provide a direct mechanistic link between apicobasal polarity and the cell cycle, which may explain how proliferation is favored over differentiation in polarized neural stem cells. PMID:25490266

  19. Gravity and light control of the developmental polarity of regenerating protoplasts isolated from prothallial cells of the fern Ceratopteris richardii

    NASA Technical Reports Server (NTRS)

    Edwards, E. S.; Roux, S. J.

    1998-01-01

    A procedure has been developed for isolating protoplasts from prothalli of Ceratopteris richardii which can be cultured and are capable of regeneration. Protoplasts were isolated from 2-week-old gametophytes in a medium containing wall-digesting enzymes in 0.5 M sucrose, followed by purification of the released protoplasts by floating them up into a 0.5 M sorbitol layer. Regeneration occurred over a period of 10-24 days, and, under optimal osmotic conditions, followed the developmental pattern seen during spore germination, in that the first division gave rise to a primary rhizoid. Thus, prothallial protoplasts are comparable to germinating spores as suitable models for studies of developmental polarity in single cells. As in germinating spores, the polarity of development in regenerating protoplasts is influenced by the vectors of gravity and unilateral light. However, the relative influence of light in fixing this polarity is greater in regenerating protoplasts, while in germinating spores, the influence of gravity is greater.

  20. Polarization-controlled evolution of light transverse modes and associated Pancharatnam geometric phase in orbital angular momentum

    SciTech Connect

    Karimi, Ebrahim; Marrucci, Lorenzo; Slussarenko, Sergei; Piccirillo, Bruno; Santamato, Enrico

    2010-05-15

    We present an easy, efficient, and fast method to generate arbitrary linear combinations of light orbital angular-momentum eigenstates l={+-}2 starting from a linearly polarized TEM{sub 00} laser beam. The method exploits the spin-to-orbital angular-momentum conversion capability of a liquid-crystal-based q plate and a Dove prism inserted into a Sagnac polarizing interferometer. The nominal generation efficiency is 100%, being limited only by reflection and scattering losses in the optical components. When closed paths are followed on the polarization Poincare sphere of the input beam, the associated Pancharatnam geometric phase is transferred unchanged to the orbital angular momentum state of the output beam.

  1. Tailoring the photocurrent in BaTiO3/Nb:SrTiO3 photoanodes by controlled ferroelectric polarization

    NASA Astrophysics Data System (ADS)

    Rioult, M.; Datta, S.; Stanescu, D.; Stanescu, S.; Belkhou, R.; Maccherozzi, F.; Magnan, H.; Barbier, A.

    2015-09-01

    We demonstrate on prototypical samples containing a ferroelectric layer (BaTiO3/Nb:SrTiO3) that the efficiency of the system, used as photoanode, substantially depends on the polarization state of the ferroelectric layer. We show a significant increase of the photocurrent by a factor larger than 2 when the BaTiO3 film is downward polarized. We explain this finding by the presence of an internal electric field which favors the separation of photo-generated charges.

  2. Polarization of barcode readers

    NASA Astrophysics Data System (ADS)

    Reiley, Daniel J.

    1998-02-01

    In high-quality barcode readers, specular reflection from shiny barcodes is blocked by using a polarized scan laser and a crossed polarizer in front of the detector. When complex scanning geometries are required, the polarization properties of the mirrors in the system can become a limiting factor in system performance. Polarization raytracing allows systems such as barcode readers, LIDAR systems, and other polarization-critical system to be accurately characterized. Polarization raytracing often requires the use of local, ray-based coordinate system for expressing rays' polarization states, yet the choice of coordinate system can have important implications on system analysis. An example is presented in which specular reflection is controlled in a barcode reader by using reflection-enhanced coatings on only one of the four set of the mirrors in the system. The coordinate system used to express rays' polarization states in the example system provides useful lessons for other systems. The other analytical methods used in this example can be applied to a variety of scanning systems.

  3. Polarization developments

    SciTech Connect

    Prescott, C.Y.

    1993-07-01

    Recent developments in laser-driven photoemission sources of polarized electrons have made prospects for highly polarized electron beams in a future linear collider very promising. This talk discusses the experiences with the SLC polarized electron source, the recent progress with research into gallium arsenide and strained gallium arsenide as a photocathode material, and the suitability of these cathode materials for a future linear collider based on the parameters of the several linear collider designs that exist.

  4. Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. http://pos.sissa.it 10 Gb/s Radiation-Hard VCSEL Array Driver

    E-print Network

    Gan, K. K.

    -NonCommercial-ShareAlike Licence. http://pos.sissa.it 10 Gb/s Radiation-Hard VCSEL Array Driver K.K. Gan1 , H.P. Kagan, R.D. Kass Surface Emitting Laser) array driver operating at 10 Gb/s per channel, yielding an aggregated bandwidth of 120 Gb/s. The design of the 10 Gb/s array driver ASIC is based on a prototype ASIC for driving a VCSEL

  5. Real-time, continuous, fluorescence sensing in a freely-moving subject with an implanted hybrid VCSEL/CMOS biosensor.

    PubMed

    O'Sullivan, Thomas D; Heitz, Roxana T; Parashurama, Natesh; Barkin, David B; Wooley, Bruce A; Gambhir, Sanjiv S; Harris, James S; Levi, Ofer

    2013-01-01

    Performance improvements in instrumentation for optical imaging have contributed greatly to molecular imaging in living subjects. In order to advance molecular imaging in freely moving, untethered subjects, we designed a miniature vertical-cavity surface-emitting laser (VCSEL)-based biosensor measuring 1cm(3) and weighing 0.7g that accurately detects both fluorophore and tumor-targeted molecular probes in small animals. We integrated a critical enabling component, a complementary metal-oxide semiconductor (CMOS) read-out integrated circuit, which digitized the fluorescence signal to achieve autofluorescence-limited sensitivity. After surgical implantation of the lightweight sensor for two weeks, we obtained continuous and dynamic fluorophore measurements while the subject was un-anesthetized and mobile. The technology demonstrated here represents a critical step in the path toward untethered optical sensing using an integrated optoelectronic implant. PMID:24009996

  6. A multiple-input-multiple-output visible light communication system based on VCSELs and spatial light modulators.

    PubMed

    Lu, Hai-Han; Lin, Ying-Pyng; Wu, Po-Yi; Chen, Chia-Yi; Chen, Min-Chou; Jhang, Tai-Wei

    2014-02-10

    A multiple-input-multiple-output (MIMO) visible light communication (VLC) system employing vertical cavity surface emitting laser (VCSEL) and spatial light modulators (SLMs) with 16-quadrature amplitude modulation (QAM)-orthogonal frequency-division multiplexing (OFDM) modulating signal is proposed and experimentally demonstrated. The transmission capacity of system is significantly increased by space-division demultiplexing scheme. With the assistance of low noise amplifier (LNA) and data comparator, good bit error rate (BER) performance, clear constellation map, and clear eye diagram are achieved for each optical channel. Such a MIMO VLC system would be attractive for providing services including data and telecommunication services. Our proposed system is suitably applicable to the lightwave communication system in wireless transmission. PMID:24663637

  7. The VCSEL-based array optical transmitter (ATx) development towards 120-Gbps link for collider detector: development update

    NASA Astrophysics Data System (ADS)

    Guo, D.; Liu, C.; Chen, J.; Chramowicz, J.; Gong, D.; Hou, S.; Huang, D.; Jin, G.; Li, X.; Liu, T.; Prosser, A.; Teng, P. K.; Ye, J.; Zhou, Y.; You, Y.; Xiang, A. C.; Liang, H.

    2015-01-01

    A compact radiation-tolerant array optical transmitter module (ATx) is developed to provide data transmission up to 10Gbps per channel with 12 parallel channels for collider detector applications. The ATx integrates a Vertical Cavity Surface-Emitting Laser (VCSEL) array and driver circuitry for electrical to optical conversion, an edge warp substrate for the electrical interface and a micro-lens array for the optical interface. This paper reports the continuing development of the ATx custom package. A simple, high-accuracy and reliable active-alignment method for the optical coupling is introduced. The radiation-resistance of the optoelectronic components is evaluated and the inclusion of a custom-designed array driver is discussed.

  8. Real-time, continuous, fluorescence sensing in a freely-moving subject with an implanted hybrid VCSEL/CMOS biosensor

    PubMed Central

    O’Sullivan, Thomas D.; Heitz, Roxana T.; Parashurama, Natesh; Barkin, David B.; Wooley, Bruce A.; Gambhir, Sanjiv S.; Harris, James S.; Levi, Ofer

    2013-01-01

    Performance improvements in instrumentation for optical imaging have contributed greatly to molecular imaging in living subjects. In order to advance molecular imaging in freely moving, untethered subjects, we designed a miniature vertical-cavity surface-emitting laser (VCSEL)-based biosensor measuring 1cm3 and weighing 0.7g that accurately detects both fluorophore and tumor-targeted molecular probes in small animals. We integrated a critical enabling component, a complementary metal-oxide semiconductor (CMOS) read-out integrated circuit, which digitized the fluorescence signal to achieve autofluorescence-limited sensitivity. After surgical implantation of the lightweight sensor for two weeks, we obtained continuous and dynamic fluorophore measurements while the subject was un-anesthetized and mobile. The technology demonstrated here represents a critical step in the path toward untethered optical sensing using an integrated optoelectronic implant. PMID:24009996

  9. High-power Yb-fiber comb with feed-forward control of nonlinear-polarization-rotation mode-locking and large-mode-area fiber amplification.

    PubMed

    Yan, Ming; Li, Wenxue; Yang, Kangwen; Zhou, Hui; Shen, Xuling; Zhou, Qian; Ru, Qitian; Bai, Dongbi; Zeng, Heping

    2012-05-01

    We report on a simple scheme to precisely control carrier-envelope phase of a nonlinear-polarization-rotation mode-locked self-started Yb-fiber laser system with an average output power of ?7??W and a pulse width of 130 fs. The offset frequency was locked to the repetition rate of ?64.5??MHz with a relative linewidth of ?1.4??MHz by using a self-referenced feed-forward scheme based on an acousto-optic frequency shifter. The phase noise and timing jitter were calculated to be 370 mrad and 120 as, respectively. PMID:22555721

  10. Development of polarization-controlled multi-pass Thomson scattering system in the GAMMA 10 tandem mirror

    SciTech Connect

    Yoshikawa, M.; Morimoto, M.; Shima, Y.; Kohagura, J.; Sakamoto, M.; Nakashima, Y.; Imai, T.; Yasuhara, R.; Yamada, I.; Kawahata, K.; Funaba, H.; Minami, T.

    2012-10-15

    In the GAMMA 10 tandem mirror, the typical electron density is comparable to that of the peripheral plasma of torus-type fusion devices. Therefore, an effective method to increase Thomson scattering (TS) signals is required in order to improve signal quality. In GAMMA 10, the yttrium-aluminum-garnet (YAG)-TS system comprises a laser, incident optics, light collection optics, signal detection electronics, and a data recording system. We have been developing a multi-pass TS method for a polarization-based system based on the GAMMA 10 YAG TS. To evaluate the effectiveness of the polarization-based configuration, the multi-pass system was installed in the GAMMA 10 YAG-TS system, which is capable of double-pass scattering. We carried out a Rayleigh scattering experiment and applied this double-pass scattering system to the GAMMA 10 plasma. The integrated scattering signal was made about twice as large by the double-pass system.

  11. Enhancement of response of a bistable VCSEL to modulated orthogonal optical feedback by vibrational resonance.

    PubMed

    Chizhevsky, V N

    2012-11-01

    It is experimentally demonstrated that the response of a bistable vertical-cavity surface-emitting laser at a selected polarization to the effect of the modulated optical feedback at the orthogonal polarization can be considerably enhanced by the additional periodic current modulation via vibrational resonance. It shows up as a nonmonotonic dependence of the response at the frequency of the modulated optical feedback as a function of the amplitude of the current modulation. In such conditions the laser response can be amplified more than 80 times for a weak optical feedback. At the optimal amplitude of the current modulation a complete synchronization of optical switchings between polarization states with modulated optical feedback is observed. The effect of asymmetry of a bistable quasi-potential is also experimentally demonstrated. PMID:23114304

  12. Polarity protein Par3 controls B-cell receptor dynamics and antigen extraction at the immune synapse

    PubMed Central

    Reversat, Anne; Yuseff, Maria-Isabel; Lankar, Danielle; Malbec, Odile; Obino, Dorian; Maurin, Mathieu; Penmatcha, Naga Venkata Gayathri; Amoroso, Alejandro; Sengmanivong, Lucie; Gundersen, Gregg G.; Mellman, Ira; Darchen, François; Desnos, Claire; Pierobon, Paolo; Lennon-Duménil, Ana-Maria

    2015-01-01

    B-cell receptor (BCR) engagement with surface-tethered antigens leads to the formation of an immune synapse, which facilitates antigen uptake for presentation to T-lymphocytes. Antigen internalization and processing rely on the early dynein-dependent transport of BCR–antigen microclusters to the synapse center, as well as on the later polarization of the microtubule-organizing center (MTOC). MTOC repositioning allows the release of proteases and the delivery of MHC class II molecules at the synapse. Whether and how these events are coordinated have not been addressed. Here we show that the ancestral polarity protein Par3 promotes BCR–antigen microcluster gathering, as well as MTOC polarization and lysosome exocytosis, at the synapse by facilitating local dynein recruitment. Par3 is also required for antigen presentation to T-lymphocytes. Par3 therefore emerges as a key molecule in the coupling of the early and late events needed for efficient extraction and processing of immobilized antigen by B-cells. PMID:25631815

  13. Polar Bear

    USGS Publications Warehouse

    Amstrup, S.D.; DeMaster

    1988-01-01

    Polar bears are long-lived, late-maturing carnivores that have relatively low rates of reproduction and natural mortality. Their populations are susceptible to disturbance from human activities, such as the exploration and development of mineral resources or hunting. Polar bear populations have been an important renewable resource available to coastal communities throughout the Arctic for thousands of years.

  14. 10??m/25??Gbps LiFi transmission system based on a two-stage injection-locked 680??nm VCSEL transmitter.

    PubMed

    Lu, Hai-Han; Li, Chung-Yi; Chu, Chien-An; Lu, Ting-Chien; Chen, Bo-Rui; Wu, Chang-Jen; Lin, Dai-Hua

    2015-10-01

    A 10??m/25??Gbps light-based WiFi (LiFi) transmission system based on a two-stage injection-locked 680 nm vertical-cavity surface-emitting laser (VCSEL) transmitter is proposed. A LiFi transmission system with a data rate of 25 Gbps is experimentally demonstrated over a 10 m free-space link. To the best of our knowledge, it is the first time a two-stage injection-locked 680 nm VCSEL transmitter in a 10??m/25??Gbps LiFi transmission system has been employed. Impressive bit error rate performance and a clear eye diagram are achieved in the proposed systems. Such a 10??m/25??Gbps LiFi transmission system provides the advantage of a communication link for higher data rates that could accelerate the deployment of visible laser light communication. PMID:26421582

  15. High-speed wavelength-division multiplexing and demultiplexing using monolithic quasi-planar VCSEL and resonant photodetector arrays with strained InGaAs quantum wells

    SciTech Connect

    Zhou, Y.; Cheng, J.; Allerman, A.A.

    2000-02-01

    The authors demonstrate the high-speed (gigabit-per-second) operation of a wavelength-division-multiplexed optical interconnect, which is implemented by multiplexing the optical data from a multiple-wavelength vertical-cavity surface-emitting laser (VCSEL) array into a single optical fiber, and demultiplexing the composite data stream using an array of resonance-enhanced photodetectors (REPD's) with matching resonance wavelengths. By using VCSEL's and REPD's with a new quasi-planar oxide-confinement design for improved high-speed performance, and using strained InGaAs-GaAs quantum wells to achieve a better tradeoff between optical responsivity and wavelength selectivity, wavelength-division-multiplexing (WDM) operation has been demonstrated under 1-Gb/s data modulation, with an optical crosstalk rejection ratio of better than {minus}10 dB for wavelength channels that are spaced 2 nm apart.

  16. High-temperature operating 894.6nm-VCSELs with extremely low threshold for Cs-based chip scale atomic clocks.

    PubMed

    Zhang, Jianwei; Zhang, Xing; Zhu, Hongbo; Zhang, Jian; Ning, Yongqiang; Qin, Li; Wang, Lijun

    2015-06-01

    We report on the design and fabrication of 894.6nm vertical-cavity surface-emitting lasers (VCSELs) with extremely low threshold at high temperatures, for use in chip-scale Cs atomic clocks. A new design method based on the analysis of the threshold gain and the desired carrier density for different active region structures was proposed to gain the low transparent current density. The increase of the threshold current at higher temperatures was successfully suppressed by introducing the large gain-cavity detuning of VCSEL. By detuning the gain-cavity mode to be -11nm, the minimum threshold current of only 0.23mA at 70 °C was achieved. The operating temperature for emitting the wavelength of 894.6nm was 110 °C, with the single mode suppression ratio (SMSR) of more than 25dB and the threshold current of only 0.32mA. PMID:26072835

  17. Polar Glaciology

    NASA Technical Reports Server (NTRS)

    Robin, G. D.

    1984-01-01

    Two fields of research on polar ice sheets are likely to be of dominant interest during the 1990s. These are: the role of polar ice sheets in the hydrological cycle ocean-atmosphere-ice sheets-oceans, especially in relation to climate change; and the study and interpretation of material in deep ice cores to provide improved knowledge of past climates and of the varying levels of atmospheric constituents such as CO2, NOx, SO2, aerosols, etc., over the past 200,000 years. Both topics require a better knowledge of ice dynamics. Many of the studies that should be undertaken in polar regions by Earth Observing System require similar instruments and techniques to those used elsewhere over oceans and inland surfaces. However to study polar regions two special requirements need to be met: Earth Observing System satellite(s) need to be in a sufficiently high inclination orbit to cover most of the polar regions. Instruments must also be adapted, often by relatively limited changes, to give satisfactory data over polar ice. The observational requirements for polar ice sheets in the 1990s are summarized.

  18. EDITORIAL: Polarization Optics

    NASA Astrophysics Data System (ADS)

    Turunen, Jari; Friesem, Asher A.; Friberg, Ari T.

    2004-03-01

    This special issue on Polarization Optics contains one review article and 23 research papers, many of which are based on presentations at the International Commission for Optics Topical Meeting on Polarization Optics, held in Polvijärvi, Finland, between 30 June and 3 July 2003. While this issue should not in any sense be considered as a `proceedings' of this meeting, the possibility of submitting papers to it was widely advertised during the meeting, which was attended by a large fraction of prominent scientists in the field of polarization optics. Thus the quality of papers in this special issue is high. In announcing both the meeting and this special issue, we emphasized that the concept of `polarization optics' should be understood in a wide sense. In fact, all contributions dealing with the vectorial nature of light were welcome. As a result, the papers included here cover a wide range of different aspects of linear and nonlinear polarization optics. Both theoretical and experimental features are discussed. We are pleased to see that the conference and this special issue both reflect the wide diversity of important and novel polarization phenomena in optics. The papers in this special issue, and other recently published works, demonstrate that even though polarization is a fundamental property of electromagnetic fields, interest in it is rapidly increasing. The fundamental relations between partial coherence and partial polarization are currently under vigorous research in electromagnetic coherence theory. In diffractive optics it has been found that the exploitation of the vectorial nature of light can be of great benefit. Fabrication of sophisticated, spatially variable polarization-control elements is becoming possible with the aid of nanolithography. Polarization singularities and the interplay of bulk properties and topology in nanoscale systems have created much enthusiasm. In nonlinear optics, the second harmonic waves generated on reflection and transmission of intense light enable research into the chirality of nanogratings. Pump-probe techniques allow one to visualize the effects of the nanostructure topology on the surface mode excitation. In quantum optics the coherent control of polarization may lead to new and fascinating applications. Some authors of invited papers at the conference have written review-type introductory sections—they were encouraged to do so—but all contributions are genuine research papers with original results, and were judged according to the normal publication criteria of the journal. It is our pleasure to thank all authors for making this a splendid special issue of Journal of Optics A: Pure and Applied Optics.

  19. Quad 14 Gbps L-band VCSEL-based system for WDM migration of 4-lanes 56 Gbps optical data links.

    PubMed

    Estaran, Jose; Rodes, Roberto; Pham, Tien Thang; Ortsiefer, Markus; Neumeyr, Christian; Rosskopf, Jürgen; Monroy, Idelfonso Tafur

    2012-12-17

    We report on migrating multiple-lane link into an L-band VCSEL-based WDM system. Experimental validation achieves successful transmission over 10 km of SMF at 4x14Gbps. Inter-channel crosstalk penalty is observed to be less than 0.5 dB and a transmission penalty around 1 dB. The power budget margin ranges within 6 dB and 7 dB. PMID:23263089

  20. Epidermal Growth Factor Signalling Controls Myosin II Planar Polarity to Orchestrate Convergent Extension Movements during Drosophila Tubulogenesis

    PubMed Central

    Bunt, Stephanie; Bischoff, Marcus; VijayRaghavan, Krishnaswamy; Skaer, Helen

    2014-01-01

    Most epithelial tubes arise as small buds and elongate by regulated morphogenetic processes including oriented cell division, cell rearrangements, and changes in cell shape. Through live analysis of Drosophila renal tubule morphogenesis we show that tissue elongation results from polarised cell intercalations around the tubule circumference, producing convergent-extension tissue movements. Using genetic techniques, we demonstrate that the vector of cell movement is regulated by localised epidermal growth factor (EGF) signalling from the distally placed tip cell lineage, which sets up a distal-to-proximal gradient of pathway activation to planar polarise cells, without the involvement for PCP gene activity. Time-lapse imaging at subcellular resolution shows that the acquisition of planar polarity leads to asymmetric pulsatile Myosin II accumulation in the basal, proximal cortex of tubule cells, resulting in repeated, transient shortening of their circumferential length. This repeated bias in the polarity of cell contraction allows cells to move relative to each other, leading to a reduction in cell number around the lumen and an increase in tubule length. Physiological analysis demonstrates that animals whose tubules fail to elongate exhibit abnormal excretory function, defective osmoregulation, and lethality. PMID:25460353

  1. Multispectral polarized scene projector (MPSP)

    NASA Astrophysics Data System (ADS)

    Yu, Haiping; Wei, Hong; Guo, Lei; Wang, Shenggang; Li, Le; Lippert, Jack R.; Serati, Steve; Gupta, Neelam; Carlen, Frank R.

    2011-06-01

    This newly developed prototype Multispectral Polarized Scene Projector (MPSP), configured for the short wave infrared (SWIR) regime, can be used for the test & evaluation (T&E) of spectro-polarimetric imaging sensors. The MPSP system generates both static and video images (up to 200 Hz) with 512×512 spatial resolution with active spatial, spectral, and polarization modulation with controlled bandwidth. It projects input SWIR radiant intensity scenes from stored memory with user selectable wavelength (850-1650 nm) and bandwidth (12-100 nm), as well as polarization states (six different states) controllable on a pixel by pixel basis. The system consists of one spectrally tunable liquid crystal filter with variable bandpass, and multiple liquid crystal on silicon (LCoS) spatial light modulators (SLMs) for intensity control and polarization modulation. In addition to the spectro-polarimetric sensor test, the instrument also simulates polarized multispectral images of military scenes/targets for hardware-in-the loop (HIL) testing.

  2. Direct generation of 2-ps blue pulses from gain-switched InGaN VCSEL assessed by up-conversion technique

    PubMed Central

    Asahara, Akifumi; Chen, Shaoqiang; Ito, Takashi; Yoshita, Masahiro; Liu, Wenjie; Zhang, Baoping; Suemoto, Tohru; Akiyama, Hidefumi

    2014-01-01

    Ultra-short pulses in blue region generated from compact and low-cost semiconductor lasers have attracted much attention for a wide variety of applications. Nitride-based vertical-cavity surface-emitting lasers (VCSELs), having intrinsic high material gain and short cavities, favor the generation of ultra-short blue pulses via a simple gain-switching technique. In this study, we fabricated a single-mode InGaN VCSEL consisting of 10-period InGaN/GaN quantum wells (QWs). The output pulses were evaluated accurately with an up-conversion measurement system having time resolution of 0.12?ps. We demonstrated that ultra-short blue pulses, as short as 2.2?ps at 3.4?K and 4.0?ps at room temperature, were generated from the gain-switched InGaN VCSEL via impulsive optical pumping, without any post-processing. The gain-switched pulses we obtained should greatly promote the development of ultra-short blue pulse generation. In addition, this successful assessment demonstrates the up-conversion technique's usefulness for characterizing ultra-short blue pulses from semiconductor lasers. PMID:25236162

  3. Direct generation of 2-ps blue pulses from gain-switched InGaN VCSEL assessed by up-conversion technique.

    PubMed

    Asahara, Akifumi; Chen, Shaoqiang; Ito, Takashi; Yoshita, Masahiro; Liu, Wenjie; Zhang, Baoping; Suemoto, Tohru; Akiyama, Hidefumi

    2014-01-01

    Ultra-short pulses in blue region generated from compact and low-cost semiconductor lasers have attracted much attention for a wide variety of applications. Nitride-based vertical-cavity surface-emitting lasers (VCSELs), having intrinsic high material gain and short cavities, favor the generation of ultra-short blue pulses via a simple gain-switching technique. In this study, we fabricated a single-mode InGaN VCSEL consisting of 10-period InGaN/GaN quantum wells (QWs). The output pulses were evaluated accurately with an up-conversion measurement system having time resolution of 0.12 ps. We demonstrated that ultra-short blue pulses, as short as 2.2 ps at 3.4 K and 4.0 ps at room temperature, were generated from the gain-switched InGaN VCSEL via impulsive optical pumping, without any post-processing. The gain-switched pulses we obtained should greatly promote the development of ultra-short blue pulse generation. In addition, this successful assessment demonstrates the up-conversion technique's usefulness for characterizing ultra-short blue pulses from semiconductor lasers. PMID:25236162

  4. Multigigabit/s perfluorinated graded-index plastic-optical-fiber data links with butt-coupled single-mode InGaAs VCSEL

    NASA Astrophysics Data System (ADS)

    Mederer, Felix; Jaeger, Roland; Schnitzer, Peter; Unold, Heiko J.; Kicherer, Max; Ebeling, Karl J.; Naritomi, Masaki; Yoshida, Ryouta

    1999-11-01

    Vertical-cavity surface-emitting lasers (VCSELs) with emission wavelengths in the range from 850 nm to 950 nm are highly attractive light sources for low-cost, high-speed data transmission over several hundred meters of perfluorinated graded-index plastic-optical fibers (GI- POFs). Multi-Gigabit/s data transmission over common PMA- based step-index POFs is generally limited to several meters predominantly due to dispersion. Here, we demonstrate 3 Gbit/s and 7 Gbit/s pseudo-random-bit-sequence non-return- to-zero data transmission over 80 m perfluorinated GI-POF made of CYTOP using a single mode butt-coupled selectively oxidized InGaAs VCSEL source emitting at 935 nm emission wavelength. For 3 Gbit/s data rather the received optical power for a bit error rate (BER) of 10-11 is -22.5 dBm for back-to-back (BTB). A power penalty of 1 dB is found for transmission over 100 m graded-index multimode glass fiber and 2 dB for 80 m GI-POF for 80 m GI- POF transmission. Reduced power penalty observed at 7 Gbit/s is attributed to the restricted modulation bandwidth of the VCSEL used in the experiment.

  5. Tunable Polarization of Spin Polarized Current by Magnetic Field

    SciTech Connect

    Joo, S.; Kim, K.; Lee, J.; Kim, T.; Rhie, K.; Hong, J.; Shin, K-H.

    2010-10-10

    The spin polarization of a high g-factor bulk semiconductor is theoretically investigated in the presence of a magnetic field parallel to a driving electric field. Calculations have been carried out using the energy-dependent relaxation time approximation in association with spin-flip scattering. As the magnitude of the magnetic field increases, the spin-polarized current alternates between the spin-up and spin-down states for the low spin-scattering system. This implies that the current polarization can be tuned by controlling the magnetic field strength, suggesting possible applications to spintronic devices. An experimental method for investigating alternative current polarization is also considered.

  6. Polarization Imaging Apparatus

    NASA Technical Reports Server (NTRS)

    Zou, Yingyin K.; Chen, Qiushui

    2010-01-01

    A polarization imaging apparatus has shown promise as a prototype of instruments for medical imaging with contrast greater than that achievable by use of non-polarized light. The underlying principles of design and operation are derived from observations that light interacts with tissue ultrastructures that affect reflectance, scattering, absorption, and polarization of light. The apparatus utilizes high-speed electro-optical components for generating light properties and acquiring polarization images through aligned polarizers. These components include phase retarders made of OptoCeramic (registered TradeMark) material - a ceramic that has a high electro-optical coefficient. The apparatus includes a computer running a program that implements a novel algorithm for controlling the phase retarders, capturing image data, and computing the Stokes polarization images. Potential applications include imaging of superficial cancers and other skin lesions, early detection of diseased cells, and microscopic analysis of tissues. The high imaging speed of this apparatus could be beneficial for observing live cells or tissues, and could enable rapid identification of moving targets in astronomy and national defense. The apparatus could also be used as an analysis tool in material research and industrial processing.

  7. Polarizing cues.

    PubMed

    Nicholson, Stephen P

    2012-01-01

    People categorize themselves and others, creating ingroup and outgroup distinctions. In American politics, parties constitute the in- and outgroups, and party leaders hold sway in articulating party positions. A party leader's endorsement of a policy can be persuasive, inducing co-partisans to take the same position. In contrast, a party leader's endorsement may polarize opinion, inducing out-party identifiers to take a contrary position. Using survey experiments from the 2008 presidential election, I examine whether in- and out-party candidate cues—John McCain and Barack Obama—affected partisan opinion. The results indicate that in-party leader cues do not persuade but that out-party leader cues polarize. This finding holds in an experiment featuring President Bush in which his endorsement did not persuade Republicans but it polarized Democrats. Lastly, I compare the effect of party leader cues to party label cues. The results suggest that politicians, not parties, function as polarizing cues. PMID:22400143

  8. Morphology and composition controlled growth of polar c-axis and nonpolar m-axis well-aligned ternary III-nitride nanotube arrays

    NASA Astrophysics Data System (ADS)

    Li, Huijie; Zhao, Guijuan; Kong, Susu; Han, Dongyue; Wei, Hongyuan; Wang, Lianshan; Chen, Zhen; Yang, Shaoyan

    2015-10-01

    Control over the nanostructure morphology and growth orientation is in high demand for fundamental research and technological applications. Herein we report a general strategy to fabricate polar c-axis and nonpolar m-axis well-aligned III-nitride ternary nanotube arrays with controllable morphologies and compositions. By depositing AlN on the InN nanorod array templates and thermally removing the InN templates, InAlN nanotubes can be obtained. Polar c-axis and nonpolar m-axis nanotubes were formed on the c- and r-plane sapphire substrates, respectively. The nanotubes are single crystalline and highly ordered on the substrates, as revealed by X-ray diffraction, electron microscopy, and selected area electron microscopy characterization. It was found that the In droplets on top of the InN nanorods play a critical role in controlling the morphology of the nanotubes. By keeping or removing the In droplets, the obtained nanotubes exhibited both ends open or only one end open. And by varying the AlN deposition temperature, the In composition in the nanotubes can be changed from 0 to 0.29. The nanotube synthesis method is simple and can be applied to the formation of other III-nitride ternary (InGaN, and AlGaN) or quaternary (InAlGaN) alloy nanotube arrays.Control over the nanostructure morphology and growth orientation is in high demand for fundamental research and technological applications. Herein we report a general strategy to fabricate polar c-axis and nonpolar m-axis well-aligned III-nitride ternary nanotube arrays with controllable morphologies and compositions. By depositing AlN on the InN nanorod array templates and thermally removing the InN templates, InAlN nanotubes can be obtained. Polar c-axis and nonpolar m-axis nanotubes were formed on the c- and r-plane sapphire substrates, respectively. The nanotubes are single crystalline and highly ordered on the substrates, as revealed by X-ray diffraction, electron microscopy, and selected area electron microscopy characterization. It was found that the In droplets on top of the InN nanorods play a critical role in controlling the morphology of the nanotubes. By keeping or removing the In droplets, the obtained nanotubes exhibited both ends open or only one end open. And by varying the AlN deposition temperature, the In composition in the nanotubes can be changed from 0 to 0.29. The nanotube synthesis method is simple and can be applied to the formation of other III-nitride ternary (InGaN, and AlGaN) or quaternary (InAlGaN) alloy nanotube arrays. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr04524j

  9. Normalized Polarization Ratios for the Analysis of Cell Polarity

    PubMed Central

    Shimoni, Raz; Pham, Kim; Yassin, Mohammed; Ludford-Menting, Mandy J.; Gu, Min; Russell, Sarah M.

    2014-01-01

    The quantification and analysis of molecular localization in living cells is increasingly important for elucidating biological pathways, and new methods are rapidly emerging. The quantification of cell polarity has generated much interest recently, and ratiometric analysis of fluorescence microscopy images provides one means to quantify cell polarity. However, detection of fluorescence, and the ratiometric measurement, is likely to be sensitive to acquisition settings and image processing parameters. Using imaging of EGFP-expressing cells and computer simulations of variations in fluorescence ratios, we characterized the dependence of ratiometric measurements on processing parameters. This analysis showed that image settings alter polarization measurements; and that clustered localization is more susceptible to artifacts than homogeneous localization. To correct for such inconsistencies, we developed and validated a method for choosing the most appropriate analysis settings, and for incorporating internal controls to ensure fidelity of polarity measurements. This approach is applicable to testing polarity in all cells where the axis of polarity is known. PMID:24963926

  10. Polarization compensator for optical communications

    NASA Technical Reports Server (NTRS)

    Fitzmaurice, M. W.; Abshire, J. B. (inventors)

    1976-01-01

    An optical data communication system is provided whereby two orthogonal polarization states of a light beam carrier correspond to digital states. In such a system, automatic polarization compensation is provided by applying a dither modulating voltage to a cell exhibiting the electro-optic effect. The cell controls the relative phase of electric field components of an input light beam enabling the dither frequency component of the difference of the instantaneous powers in the two polarization states to be coherently detected. A signal derived from the coherent detection process is fed back to the cell via an integrator to form polarization bias compensating servo loop ot Type 1.

  11. Statistical study of Subauroral Polarization Streams (SAPS): Solar wind, ionospheric control and its effect on the thermosphere

    NASA Astrophysics Data System (ADS)

    Wang, H.; Luhr, H.; Ridley, A. J.; Ma, S.

    2011-12-01

    The effects of cross-polar cap potential (CPCP) and subauroral flux tube-integrated conductivity on the spatial distribution of Subauroral Polarization Streams (SAPS) have been investigated by using DMSP observations. For higher flux tube-integrated conductivity the SAPS tend to occur more poleward than for lower conductivity. The CPCP averaged over 15 min prior to the SAPS correlates best with the SAPS peak velocities. The high-latitude CPCP has a stronger effect on SAPS velocities for low integrated conductivity than for high conductivity. With coordinated CHAMP and DMSP observations we have further investigated the relationship between SAPS, ionospheric Hall current (electrojet), upper thermospheric zonal wind, and mass density at subauroral regions in the dusk and premidnight sectors. For comparison, we have also analyzed the same parameters as a function of magnetic latitude (30°-80° magnetic latitude) during nonSAPS periods. Both neutral and plasma velocities peak at the same latitude regardless of SAPS occurrence. The neutral wind during SAPS events gets enhanced by a factor of 1.5/1.2 for Kp<4 and 1.3/1.9 for Kp?4 in the Northern/Southern Hemisphere, respectively, as compared to nonSAPS time. The velocity difference between plasma drift and neutral wind is also larger during SAPS period than during nonSAPS period, and the difference tends to increase with increasing geomagnetic activity. The peak latitude of the eastward auroral electrojet appears 1.5° poleward of SAPS during SAPS events, confirming the formation of SAPS equatorward of the high conductivity channel. The upper thermosphere is heated during SAPS periods. As a result we observe a 10% enhanced mass density at 400 km altitude with respect to periods without SAPS. In addition a density anomaly peak occurs collocated with the SAPS, displaced from the electrojet peak. We regard this as an indication for efficient thermospheric heating by ion neutral friction.

  12. 3654 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 61, NO. 11, NOVEMBER 2014 Polarity-Controllable Silicon Nanowire Transistors

    E-print Network

    De Micheli, Giovanni

    -Controllable Silicon Nanowire Transistors With Dual Threshold Voltages Jian Zhang, Student Member, IEEE, Michele De) silicon nanowires enable an unprecedented electrostatic control on the semiconductor channel that can push propose a silicon nanowire tran- sistor with three independent GAA electrodes, demonstrating, within

  13. Hepatocyte Polarity

    PubMed Central

    Treyer, Aleksandr; Müsch, Anne

    2013-01-01

    Hepatocytes, like other epithelia, are situated at the interface between the organism’s exterior and the underlying internal milieu and organize the vectorial exchange of macromolecules between these two spaces. To mediate this function, epithelial cells, including hepatocytes, are polarized with distinct luminal domains that are separated by tight junctions from lateral domains engaged in cell-cell adhesion and from basal domains that interact with the underlying extracellular matrix. Despite these universal principles, hepatocytes distinguish themselves from other nonstriated epithelia by their multipolar organization. Each hepatocyte participates in multiple, narrow lumina, the bile canaliculi, and has multiple basal surfaces that face the endothelial lining. Hepatocytes also differ in the mechanism of luminal protein trafficking from other epithelia studied. They lack polarized protein secretion to the luminal domain and target single-spanning and glycosylphosphatidylinositol-anchored bile canalicular membrane proteins via transcytosis from the basolateral domain. We compare this unique hepatic polarity phenotype with that of the more common columnar epithelial organization and review our current knowledge of the signaling mechanisms and the organization of polarized protein trafficking that govern the establishment and maintenance of hepatic polarity. The serine/threonine kinase LKB1, which is activated by the bile acid taurocholate and, in turn, activates adenosine monophosphate kinase-related kinases including AMPK1/2 and Par1 paralogues has emerged as a key determinant of hepatic polarity. We propose that the absence of a hepatocyte basal lamina and differences in cell-cell adhesion signaling that determine the positioning of tight junctions are two crucial determinants for the distinct hepatic and columnar polarity phenotypes. PMID:23720287

  14. A Bmp/Admp Regulatory Circuit Controls Maintenance and Regeneration of Dorsal-Ventral Polarity in Planarians

    E-print Network

    Reddien, Peter

    Animal embryos have diverse anatomy and vary greatly in size. It is therefore remarkable that a common signaling pathway, BMP signaling, controls development of the dorsoventral (DV) axis throughout the Bilateria [1, 2, ...

  15. The polarity protein Inturned links NPHP4 to Daam1 to control the subapical actin network in multiciliated cells.

    PubMed

    Yasunaga, Takayuki; Hoff, Sylvia; Schell, Christoph; Helmstädter, Martin; Kretz, Oliver; Kuechlin, Sebastian; Yakulov, Toma A; Engel, Christina; Müller, Barbara; Bensch, Robert; Ronneberger, Olaf; Huber, Tobias B; Lienkamp, Soeren S; Walz, Gerd

    2015-12-01

    Motile cilia polarization requires intracellular anchorage to the cytoskeleton; however, the molecular machinery that supports this process remains elusive. We report that Inturned plays a central role in coordinating the interaction between cilia-associated proteins and actin-nucleation factors. We observed that knockdown of nphp4 in multiciliated cells of the Xenopus laevis epidermis compromised ciliogenesis and directional fluid flow. Depletion of nphp4 disrupted the subapical actin layer. Comparison to the structural defects caused by inturned depletion revealed striking similarities. Furthermore, coimmunoprecipitation assays demonstrated that the two proteins interact with each other and that Inturned mediates the formation of ternary protein complexes between NPHP4 and DAAM1. Knockdown of daam1, but not formin-2, resulted in similar disruption of the subapical actin web, whereas nphp4 depletion prevented the association of Inturned with the basal bodies. Thus, Inturned appears to function as an adaptor protein that couples cilia-associated molecules to actin-modifying proteins to rearrange the local actin cytoskeleton. PMID:26644512

  16. An ultra-bright white LED based non-contact skin cancer imaging system with polarization control

    NASA Astrophysics Data System (ADS)

    Günther, A.; Basu, C.; Roth, B.; Meinhardt-Wollweber, M.

    2013-06-01

    Early detection and excision of melanoma skin cancer is crucial for a successful therapy. Dermoscopy in direct contact with the skin is routinely used for inspection, but screening is time consuming for high-risk patients with a large number of nevi. Features like symmetry, border, color and most importantly changes like growth or depigmentation of a nevus may indicate malignancy. We present a non-contact remote imaging system for human melanocytic nevi with homogenous illumination by an ultra-bright white LED. The advantage compared to established dermoscopy systems requiring direct skin contact is that deformation of raised nevi is avoided and full-body scans of the patients may time-efficiently be obtained while they are in a lying, comfortable position. This will ultimately allow for automated screening in the future. In addition, calibration of true color rendering, which is essential for distinguishing between benign and malignant lesions and to ensure reproducibility and comparison between individual check-ups in order to follow nevi evolution is implemented as well as suppression of specular highlights on the skin surface by integration of polarizing filters. Important features of the system which will be crucial for future integration into automated systems are the possibility to record images without artifacts in combination with short exposure times which both reduce image blurring caused by patient motion.

  17. Numerical simulation of temperature-dependence on distributed Bragg reflector (DBR) and performance analyses for proton-implant/oxide confined VCSEL: comparison with transmission matrix, matrix calculating methods, and Macleod model

    NASA Astrophysics Data System (ADS)

    Tsai, Hong-Mau; Tang, Shiang-Feng; Sua, Shih-Tsang; Chen, Tzu-Chiang; Chiang, Cheng-Der

    2007-02-01

    This paper mainly focuses on the simulation for temperature-dependent Distributed Bragg Reflector (DBR) of 850nm vertical cavity surface emitting laser (VCSEL) with Transmission Matrix (TMM), Matrix Calculating Methods (MCM) and Macleod Model and performance for comparison with proton-implant/oxide confined process on VCSEL. Using well-developed temperature-dependent DBR-reflectivity solver with Mathcad simulator, we have successfully compared the Macleod Model simulator with theoretical self-developed solution based on the Transmission Matrix (TMM), Matrix Calculating Methods (MCM) and find very good agreement with previous results while accounting for influences of conjugated part of refractive index and graded Al compositions of DBR materials. Moreover, optoelectronic performance of Proton-Implant/Oxide Confined 850nm VCSEL have been demonstrated on this paper using temperature-dependent power output, voltage/injection current, transverse operating wavelengths, optical spectral characteristics, slope efficiency and transverse optical modes with an approximated Marcatili's method extracted and measurement from systematically measuring experiments. Through adequate and precise LD device design and processes, we have proposed the high performance single-mode proton implanted in contrast to the oxide confined 850 nm VCSEL. Under nominal temperature-variety and keeping operating temperature of 30°C,the threshold voltage, injecting current, peak-wavelength and differential resistance of the proton implanted VCSEL with the optical aperture in the dimension of 10 ?m are 1.8 V, 3.2 mA, 851 nm and 36.8 ohm, respectively.

  18. Dynamic and static control of the optical phase of guided p-polarized light for near-field focusing at large angles of incidence

    E-print Network

    Huang, Danhong; Wellems, L David; Mozer, Henry; Gumbs, Godfrey; Cardimona, D A; Maradudin, A A

    2013-01-01

    Both dynamic and static approaches are proposed and investigated for controlling the optical phase of a p-polarized light wave that is guided through a surface-patterned metallic structure with subwavelength features. For dynamic control, field-induced transparency (FIT) from photo-excited electrons in a slit-embedded atomic system show up within a narrow frequency window for modulating the intensity of focused transmitted light in the near-field region. Based on the electromagnetic coupling, this is facilitated by surface plasmons between the two FIT-atom embedded slits. For static control, the role of surface curvature is obtained for focused transmitted light passing through a Gaussian-shaped metallic microlens embedded with a linear array of slits, in addition to a negative light-refraction pattern, which is associated with higher-diffraction modes of light, under a large angle of incidence in the near-field region. Most interesting, however, this anomalous negative light-refraction pattern becomes suppre...

  19. CONFIGURATION MANUAL POLARIZED PROTON COLLIDER AT RHIC.

    SciTech Connect

    ROSER,T.; MACKAY,W.W.; ALEKSEEV,I.; BAI,M.; BROWN,K.; BUNCE,G.; CAMERON,P.; COURANT,E.; ET AL.

    2001-03-01

    In this report, the authors present their design to accelerate and store polarized protons in RHIC, with the level of polarization, luminosity, and control of systematic errors required by the approved RHIC spin physics program. They provide an overview of the physics to be studied using RHIC with polarized proton beams, and a brief description of the accelerator systems required for the project.

  20. Configuration Manual Polarized Proton Collider at RHIC

    SciTech Connect

    Alekseev, I.; Allgower, C.; Bai, M.; Batygin, Y.; Bozano, L.; Brown, K.; Bunce, G.; Cameron, P.; Courant, E.; Erin, S.; Escallier, J.; Fischer, W.; Gupta, R.; Hatanka, K.; Huang, H.; Imai, K.; Ishihara, M.; Jain, A.; Kanavets, V.; Katayama, T.; Kawaguchi, T.; Kelly, E.; Kurita, K.; Lee, S. Y.; Luccio, A.; MacKay, W. W.; Mahler, G.; Makdisi, Y.; Mariam, F.; McGahern, W.; Morgan, G.; Muratore, J.; Okamura, M.; Peggs, S.; Pilat, F.; Ptitsin, V.; Ratner, L.; Roser, T.; Saito, N.; Satoh, H.; Shatunov, Y.; Spinka, H.; Svirida, D.; Syphers, M.; Tepikian, S.; Tominaka, T.; Tsoupas, N.; Underwood, D.; Vasiliev, A.; Wanderer, P.; Willen, E.; Wu, H.; Yokosawa, A.; Zelenski, A.

    2006-01-01

    In this report we present our design to accelerate and store polarized protons in RHIC, with the level of polarization, luminosity, and control of systematic errors required by the approved RHIC spin physics program. We provide an overview of the physics to be studied using RHIC with polarized proton beams, and a brief description of the accelerator systems required for the project.