Templated Sphere Phase Liquid Crystals for Tunable Random Lasing

PubMed Central

Chen, Ziping; Hu, Dechun; Chen, Xingwu; Zeng, Deren; Lee, Yungjui; Chen, Xiaoxian; Lu, Jiangang

2017-01-01

A sphere phase liquid crystal (SPLC) composed of three-dimensional twist structures with disclinations among them exists between isotropic phase and blue phase in a very narrow temperature range, about several degrees centigrade. A low concentration polymer template is applied to improve the thermal stability of SPLCs and broadens the temperature range to more than 448 K. By template processing, a wavelength tunable random lasing is demonstrated with dye doped SPLC. With different polymer concentrations, the reconstructed SPLC random lasing may achieve more than 40 nm wavelength continuous shifting by electric field modulation. PMID:29140283

Interference stabilization of atoms in a strong laser field for obtaining inversion and lasing in the visible and VUV frequency ranges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bogatskaya, A. V., E-mail: annabogatskaya@gmail.com; Volkova, E. A.; Popov, A. M.

2016-09-15

The interference stabilization of Rydberg atoms in strong laser fields is proposed for producing a plasma channel with the inverse population. Inversion between a group of Rydberg levels and low-lying excited levels and the ground state permits amplification and lasing in the IR, visible, and VUV frequency ranges. The lasing and light amplification processes in the plasma channel are analyzed using rate equations and the efficiency of this method is compared with that in the usual method for high harmonic generation during rescattering of electrons by a parent ion.

A cascaded silicon Raman laser

NASA Astrophysics Data System (ADS)

Rong, Haisheng; Xu, Shengbo; Cohen, Oded; Raday, Omri; Lee, Mindy; Sih, Vanessa; Paniccia, Mario

2008-03-01

One of the major advantages of Raman lasers is their ability to generate coherent light in wavelength regions that are not easily accessible with other conventional types of lasers. Recently, efficient Raman lasing in silicon in the near-infrared region has been demonstrated, showing great potential for realizing low-cost, compact, room-temperature lasers in the mid-infrared region. Such lasers are highly desirable for many applications, ranging from trace-gas sensing, environmental monitoring and biomedical analysis, to industrial process control, and free-space communications. Here we report the first experimental demonstration of cascaded Raman lasing in silicon, opening the path to extending the lasing wavelength from the near- to mid-infrared region. Using a 1,550-nm pump source, we achieve stable, continuous-wave, second-order cascaded lasing at 1,848 nm with an output power exceeding 5 mW. The laser operates in single mode, and the laser linewidth is measured to be <2.5 MHz.

Transition of lasing modes in polymeric opal photonic crystal resonating cavity.

PubMed

Shi, Lan-Ting; Zheng, Mei-Ling; Jin, Feng; Dong, Xian-Zi; Chen, Wei-Qiang; Zhao, Zhen-Sheng; Duan, Xuan-Ming

2016-06-10

We demonstrate the transition of lasing modes in the resonating cavity constructed by polystyrene opal photonic crystals and 7 wt. % tert-butyl Rhodamine B doped polymer film. Both single mode and multiple mode lasing emission are observed from the resonating cavity. The lasing threshold is determined to be 0.81  μJ/pulse for single mode lasing emission and 2.25  μJ/pulse for multiple mode lasing emission. The single mode lasing emission is attributed to photonic lasing resulting from the photonic bandgap effect of the opal photonic crystals, while the multiple mode lasing emission is assigned to random lasing due to the defects in the photonic crystals. The result would benefit the development of low threshold polymeric solid state photonic crystal lasers.

Phase-locked bifrequency Raman lasing in a double-Λ system

NASA Astrophysics Data System (ADS)

Alaeian, Hadiseh; Shahriar, M. S.

2018-05-01

We show that it is possible to realize simultaneous Raman lasing at two different frequencies using a double-Λ system pumped by a bifrequency field. The bifrequency Raman lasers are phase-locked to one another and the beat-frequency matches the energy difference between the two metastable ground states. Akin to a conventional Raman laser, the bifrequency Raman lasers are expected to be subluminal. As such, these are expected to be highly stable against perturbations in cavity length and have quantum noise limited linewidths that are far below that of a conventional laser. Because of these properties, the bifrequency Raman lasers may find important applications in precision metrology, including atomic interferometry and magnetometry. The phase-locked Raman laser pair also represent a manifestation of lasing without inversion, albeit in a configuration that produces a pair of nondegenerate lasers simultaneously. This feature may enable lasing without inversion in frequency regimes not accessible using previous techniques of lasing without inversion. To elucidate the behavior of this laser pair, we develop an analytical model that describes the stimulated Raman interaction in a double-Λ system using an effective two-level transition. The approximation is valid as long as the excited states adiabatically follow the ground states, as verified by numerical simulations. The effective model is used to identify the optimal operating conditions for the bifrequency Raman lasing process. This model may also prove useful in other potential applications of the double-Λ system, including generation of squeezed light and spatial solitons.

Nonlinear model analysis of all-optical flip-flop and inverter operations of microring laser

NASA Astrophysics Data System (ADS)

Kobayashi, Naoki; Kawamura, Yusaku; Aoki, Ryosuke; Kokubun, Yasuo

2018-03-01

We explore a theoretical model of bistability at two adjacent lasing wavelengths from an InGaAs/InGaAsP multiple quantum well (MQW) microring laser. We show that nonlinear effects on the phase and amplitude play significant roles in the lasing operations of the microring laser. Numerical simulations indicate that all-optical flip-flop operations and inverter operations can be observed within the same device by controlling the injection current. The validity of our analysis is confirmed by a comparison of the results for numerical simulations with experimental results of the lasing spectrum. We believe that the analysis presented in this paper will be useful for the future design of all-optical signal processing devices.

Optically pumped whispering-gallery mode lasing from 2-μm GaN micro-disks pivoted on Si

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yiyun; Ma, Zetao; Zhang, Xuhui

2014-06-02

2-μm micro-disks containing InGaN/GaN quantum wells supported on a tiny Si nanotip are fabricated via microsphere lithography followed by dry and wet etch processes. The micro-disks are studied by photoluminescence at both room-temperature and 10 K. Optically pumped blue lasing at room-temperature is observed via whispering-gallery modes (WGMs) with a lasing threshold as low as 8.43 mJ/cm{sup 2}. Optical resonances in the micro-disks are studied through numerical computations and finite-difference time-domain simulations. The WGMs are further confirmed through the measured broadband transmission spectrum, whose transmission minima coincide well with predicted WGM frequencies.

Segmented lasing tube for high temperature laser assembly

DOEpatents

Sawicki, Richard H.; Alger, Terry W.; Finucane, Raymond G.; Hall, Jerome P.

1996-01-01

A high temperature laser assembly capable of withstanding operating temperatures in excess of 1500.degree. C. is described comprising a segmented cylindrical ceramic lasing tube having a plurality of cylindrical ceramic lasing tube segments of the same inner and outer diameters non-rigidly joined together in axial alignment; insulation of uniform thickness surround the walls of the ceramic lasing tube; a ceramic casing, preferably of quartz, surrounding the insulation; and a fluid cooled metal jacket surrounds the ceramic casing. In a preferred embodiment, the inner surface of each of the ceramic lasing tube segments are provided with a pair of oppositely spaced grooves in the wall thereof parallel to the center axis of the segmented cylindrical ceramic lasing tube, and both of the grooves and the center axis of the segmented cylindrical ceramic lasing tube lie in a common plane, with the grooves in each ceramic lasing tube segment in circumferential alignment with the grooves in the adjoining ceramic lasing tube segments; and one or more ceramic plates, all lying in a common plane to one another and with the central axis of the segmented ceramic lasing tube, are received in the grooves to provide additional wall area in the segmented ceramic lasing tube for collision and return to ground state of metastable metal atoms within the segmented ceramic lasing tube.

Inhibiting glutamine uptake represents an attractive new strategy for treating acute myeloid leukemia

PubMed Central

Willems, Lise; Jacque, Nathalie; Jacquel, Arnaud; Neveux, Nathalie; Trovati Maciel, Thiago; Lambert, Mireille; Schmitt, Alain; Poulain, Laury; Green, Alexa S.; Uzunov, Madalina; Kosmider, Olivier; Radford-Weiss, Isabelle; Moura, Ivan Cruz; Auberger, Patrick; Ifrah, Norbert; Bardet, Valérie; Chapuis, Nicolas; Lacombe, Catherine; Mayeux, Patrick; Tamburini, Jérôme

2013-01-01

Cancer cells require nutrients and energy to adapt to increased biosynthetic activity, and protein synthesis inhibition downstream of mammalian target of rapamycin complex 1 (mTORC1) has shown promise as a possible therapy for acute myeloid leukemia (AML). Glutamine contributes to leucine import into cells, which controls the amino acid/Rag/mTORC1 signaling pathway. We show in our current study that glutamine removal inhibits mTORC1 and induces apoptosis in AML cells. The knockdown of the SLC1A5 high-affinity transporter for glutamine induces apoptosis and inhibits tumor formation in a mouse AML xenotransplantation model. l-asparaginase (l-ase) is an anticancer agent also harboring glutaminase activity. We show that l-ases from both Escherichia coli and Erwinia chrysanthemi profoundly inhibit mTORC1 and protein synthesis and that this inhibition correlates with their glutaminase activity levels and produces a strong apoptotic response in primary AML cells. We further show that l-ases upregulate glutamine synthase (GS) expression in leukemic cells and that a GS knockdown enhances l-ase–induced apoptosis in some AML cells. Finally, we observe a strong autophagic process upon l-ase treatment. These results suggest that l-ase anticancer activity and glutamine uptake inhibition are promising new therapeutic strategies for AML. PMID:24014241

Crossover from polariton lasing to exciton lasing in a strongly coupled ZnO microcavity.

PubMed

Lai, Ying-Yu; Chou, Yu-Hsun; Lan, Yu-Pin; Lu, Tien-Chang; Wang, Shing-Chung; Yamamoto, Yoshihisa

2016-02-03

Unlike conventional photon lasing, in which the threshold is limited by the population inversion of the electron-hole plasma, the exciton lasing generated by exciton-exciton scattering and the polariton lasing generated by dynamical condensates have received considerable attention in recent years because of the sub-Mott density and low-threshold operation. This paper presents a novel approach to generate both exciton and polariton lasing in a strongly coupled microcavity (MC) and determine the critical driving requirements for simultaneously triggering these two lasing operation in temperature <140 K and large negative polariton-exciton offset (<-133 meV) conditions. In addition, the corresponding lasing behaviors, such as threshold energy, linewidth, phase diagram, and angular dispersion are verified. The results afford a basis from which to understand the complicated lasing mechanisms in strongly coupled MCs and verify a new method with which to trigger dual laser emission based on exciton and polariton.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lv, Zun-Ren; Ji, Hai-Ming, E-mail: jhm@semi.ac.cn; Luo, Shuai

Large signal modulation characteristics of the simultaneous ground-state (GS) and excited-state (ES) lasing quantum dot lasers are theoretically investigated. Relaxation oscillations of ‘0 → 1’ and ‘1 → 0’ in the GS lasing region (Region I), the transition region from GS lasing to two-state lasing (Region II) and the two-state lasing region (Region III) are compared and analyzed. It is found that the overshooting power and settling time in both Regions I and III decrease as the bias current increases. However, there exist abnormal behaviors of the overshooting power and settling time in Region II owing to the occurrence ofmore » ES lasing, which lead to fuzzy eye diagrams of the GS and ES lasing. Moreover, the ES lasing in Region III possesses much better eye diagrams because of its shorter settling time and smaller overshooting power over the GS lasing in Region I.« less

LASE validation experiment: preliminary processing of relative humidity from LASE derived water vapor in the middle to upper troposphere

NASA Technical Reports Server (NTRS)

Brackett, Vincent G.; Ismail, Syed; Browell, Edward V.; Kooi, Susan A.; Clayton, Marian B.; Ferrare, Richard A.; Minnis, Patrick; Getzewich, Brian J.; Staszel, Jennifer

1998-01-01

Lidar Atmospheric Sensing Experiment (LASE) is the first fully engineered, autonomous airborne DIAL (Differentials Absorption Lidar) system to measure water vapor, aerosols, and clouds throughout the troposphere. This system uses a double-pulsed Ti:sapphire laser, which is pumped by a frequency-doubled flashlamp-pumped Nd: YAG laser, to transmit light in the 815 mn absorption band of water vapor. LASE operates by locking to a strong water vapor line and electronically tuning to any spectral position on the absorption line to choose the suitable absorption cross-section for optimum measurements over a range of concentrations in the atmosphere. During the LASE Validation Experiment, which was conducted over Wallops Island during September, 1995, LASE operated on either the strong water line for measurements in middle to upper troposphere, or on the weak water line for measurements made in the middle to lower troposphere including the boundary layer. Comparisons with water vapor measurements made by airborne dew point and frost point hygrometers, NASA/GSFC (Goddard Space Flight Center) Raman Lidar, and radiosondes showed the LASE water vapor mixing ratio measurements to have an accuracy of better than 6% or 0.01 g/kg, whichever is larger, throughout the troposphere. In addition to measuring water vapor mixing ratio profiles, LASE simultaneously measures aerosol backscattering profiles at the off-line wavelength near 815 nm from which atmospheric scattering ratio (ASR) profiles are calculated. ASR is defined as the ratio of total (aerosol + molecular) atmospheric scattering to molecular scattering. Assuming a region with very low aerosol loading can be identified, such as that typically found just below the tropopause, then the ASR can be determined. The ASR profiles are calculated by normalizing the scattering in the region containing enhanced aerosols to the expected scattering by the "clean" atmosphere at that altitude. Images of the total ASR clearly depict cloud regions, including multiple cloud layers, thin upper level cirrus, etc., throughout the troposphere. New data products that are being derived from the LASE aerosol and water measurements include: 1) aerosol extinction coefficient, 2) aerosol optical thickness, 3) precipitable water vapor, and 4) relative humidity (RH). These products can be compared with airborne in-situ, and ground and satellite remote sensing measurements,. This paper presents a preliminary examination of RH profiles in the middle to upper troposphere that are generated from LASE measured water vapor mixing ratio profiles coupled with rawinsonde profiles of temperature and pressure.

Colloidal-Quantum-Dot Ring Lasers with Active Color Control.

PubMed

le Feber, Boris; Prins, Ferry; De Leo, Eva; Rabouw, Freddy T; Norris, David J

2018-02-14

To improve the photophysical performance of colloidal quantum dots for laser applications, sophisticated core/shell geometries have been developed. Typically, a wider bandgap semiconductor is added as a shell to enhance the gain from the quantum-dot core. This shell is designed to electronically isolate the core, funnel excitons to it, and reduce nonradiative Auger recombination. However, the shell could also potentially provide a secondary source of gain, leading to further versatility in these materials. Here we develop high-quality quantum-dot ring lasers that not only exhibit lasing from both the core and the shell but also the ability to switch between them. We fabricate ring resonators (with quality factors up to ∼2500) consisting only of CdSe/CdS/ZnS core/shell/shell quantum dots using a simple template-stripping process. We then examine lasing as a function of the optical excitation power and ring radius. In resonators with quality factors >1000, excitons in the CdSe cores lead to red lasing with thresholds at ∼25 μJ/cm 2 . With increasing power, green lasing from the CdS shell emerges (>100 μJ/cm 2 ) and then the red lasing begins to disappear (>250 μJ/cm 2 ). We present a rate-equation model that can explain this color switching as a competition between exciton localization into the core and stimulated emission from excitons in the shell. Moreover, by lowering the quality factor of the cavity we can engineer the device to exhibit only green lasing. The mechanism demonstrated here provides a potential route toward color-switchable quantum-dot lasers.

Crossover from polariton lasing to exciton lasing in a strongly coupled ZnO microcavity

PubMed Central

Lai, Ying-Yu; Chou, Yu-Hsun; Lan, Yu-Pin; Lu, Tien-Chang; Wang, Shing-Chung; Yamamoto, Yoshihisa

2016-01-01

Unlike conventional photon lasing, in which the threshold is limited by the population inversion of the electron-hole plasma, the exciton lasing generated by exciton-exciton scattering and the polariton lasing generated by dynamical condensates have received considerable attention in recent years because of the sub-Mott density and low-threshold operation. This paper presents a novel approach to generate both exciton and polariton lasing in a strongly coupled microcavity (MC) and determine the critical driving requirements for simultaneously triggering these two lasing operation in temperature <140 K and large negative polariton-exciton offset (<−133 meV) conditions. In addition, the corresponding lasing behaviors, such as threshold energy, linewidth, phase diagram, and angular dispersion are verified. The results afford a basis from which to understand the complicated lasing mechanisms in strongly coupled MCs and verify a new method with which to trigger dual laser emission based on exciton and polariton. PMID:26838665

Losses, gain, and lasing in organic and perovskite active materials (Conference Presentation)

NASA Astrophysics Data System (ADS)

Pourdavoud, Neda; Riedl, Thomas J.

2016-09-01

Organic solid state lasers (OSLs) based on semiconducting polymers or small molecules have seen some significant progress over the past decade. Highly efficient organic gain materials combined with high-Q resonator geometries (distributed feedback (DFB), VCSEL, etc.) have enabled OSLs, optically pumped by simple inorganic laser diodes or even LEDs. However, some fundamental goals remain to be reached, like continuous wave (cw) operation and injection lasing. I will address various loss mechanisms related to accumulated triplet excitons or long-lived polarons that in combination with the particular photo-physics of organic gain media state the dominant road-blocks on the way to reach these goals. I will discuss the recent progress in fundamental understanding of these loss processes, which now provides a solid basis for modelling, e.g. of laser dynamics. Avenues to mitigate these fundamental loss mechanisms, e.g. by alternative materials will be presented. In this regard, a class of gain materials based on organo-lead halide perovskites re-entered the scene as light emitters, recently. Enjoying a tremendous lot of attention as active material for solution processed solar cells with a 20+% efficiency, they have recently unveiled their exciting photo-physics for lasing applications. Optically pumped lasing in these materials has been achieved. I will discuss some of the unique properties that render this class of materials a promising candidate to overcome some of the limitations of "classical" organic gain media.

Biomaterials in light amplification

NASA Astrophysics Data System (ADS)

Mysliwiec, Jaroslaw; Cyprych, Konrad; Sznitko, Lech; Miniewicz, Andrzej

2017-03-01

Biologically produced or inspired materials can serve as optical gain media, i.e. they can exhibit the phenomenon of light amplification. Some of these materials, under suitable dye-doping and optical pumping conditions, show lasing phenomena. The emerging branch of research focused on obtaining lasing action in highly disordered and highly light scattering materials, i.e. research on random lasing, is perfectly suited for biological materials. The use of biomaterials in light amplification has been extensively reported in the literature. In this review we attempt to report on progress in the development of biologically derived systems able to show the phenomena of light amplification and random lasing together with the contribution of our group to this field. The rich world of biopolymers modified with molecular aggregates and nanocrystals, and self-organized at the nanoscale, offers a multitude of possibilities for tailoring luminescent and light scattering properties that are not easily replicated in conventional organic or inorganic materials. Of particular importance and interest are light amplification and lasing, or random lasing studies in biological cells and tissues. In this review we will describe nucleic acids and their complexes employed as gain media due to their favorable optical properties and ease of manipulation. We will report on research conducted on various biomaterials showing structural analogy to nucleic acids such as fluorescent proteins, gelatins in which the first distributed feedback laser was realized, and also amyloids or silks, which, due to their dye-doped fiber-like structure, allow for light amplification. Other materials that were investigated in that respect include polysaccharides, like starch exhibiting favorable photostability in comparison to other biomaterials, and chitosan, which forms photonic crystals or cellulose. Light amplification and random lasing was not only observed in processed biomaterials but also in living cells and tissues or separated phase systems like phosphatydylcholine liposomes. All of the above-mentioned light amplification possibilities of biomaterials also have potential for several interesting applications in biology, medicine, sensing and imaging, which will be described and discussed in this review.

Resonance energy transfer process in nanogap-based dual-color random lasing

NASA Astrophysics Data System (ADS)

Shi, Xiaoyu; Tong, Junhua; Liu, Dahe; Wang, Zhaona

2017-04-01

The resonance energy transfer (RET) process between Rhodamine 6G and oxazine in the nanogap-based random systems is systematically studied by revealing the variations and fluctuations of RET coefficients with pump power density. Three working regions stable fluorescence, dynamic laser, and stable laser are thus demonstrated in the dual-color random systems. The stable RET coefficients in fluorescence and lasing regions are generally different and greatly dependent on the donor concentration and the donor-acceptor ratio. These results may provide a way to reveal the energy distribution regulars in the random system and to design the tunable multi-color coherent random lasers for colorful imaging.

Transverse mode control in proton-implanted and oxide-confined VCSELs via patterned dielectric anti-phase filters

NASA Astrophysics Data System (ADS)

Kesler, Benjamin; O'Brien, Thomas; Dallesasse, John M.

2017-02-01

A novel method for controlling the transverse lasing modes in both proton implanted and oxide-confined vertical- cavity surface-emitting lasers (VCSELs) with a multi-layer, patterned, dielectric anti-phase (DAP) filter is pre- sented. Using a simple photolithographic liftoff process, dielectric layers are deposited and patterned on individual VCSELs to modify (increase or decrease) the mirror reflectivity across the emission aperture via anti-phase reflections, creating spatially-dependent threshold material gain. The shape of the dielectric pattern can be tailored to overlap with specific transverse VCSEL modes or subsets of transverse modes to either facilitate or inhibit lasing by decreasing or increasing, respectively, the threshold modal gain. A silicon dioxide (SiO2) and titanium dioxide (TiO2) anti-phase filter is used to achieve a single-fundamental-mode, continuous-wave output power greater than 4.0 mW in an oxide-confined VCSEL at a lasing wavelength of 850 nm. A filter consisting of SiO2 and TiO2 is used to facilitate injection-current-insensitive fundamental mode and lower order mode lasing in proton implanted VCSELs at a lasing wavelength of 850 nm. Higher refractive index dielectric materials such as amorphous silicon (a-Si) can be used to increase the effectiveness of the anti-phase filter on proton implanted devices by reducing the threshold modal gain of any spatially overlapping modes. This additive, non-destructive method allows for mode selection at any lasing wavelength and for any VCSEL layer structure without the need for semiconductor etching or epitaxial regrowth. It also offers the capability of designing a filter based upon available optical coating materials.

GRIP Experiment 2010

NASA Image and Video Library

2010-08-15

Susan Kool, a researcher from the Langley Research Center, works on monitoring the Lidar Atmospheric Sensing Experiment (LASE) aboard the NASA DC-8 aircraft, Monday, Aug. 16, 2010, at Fort Lauderdale Hollywood International Airport in Fort Lauderdale, Fla. LASE probes the atmosphere using lasers and is part of the Genesis and Rapid Intensification Processes (GRIP) experiment is a NASA Earth science field experiment in 2010 that is being conducted to better understand how tropical storms form and develop into major hurricanes. Photo Credit: (NASA/Paul E. Alers)

Standoff Detection of Trace Molecules by Remote High Gain Backward Lasing in Air

DTIC Science & Technology

2016-09-17

vapor it is essential. Backward lasing from two simultaneously pumped, closely separated regions in the air provides a method for the reduction of pulse... inversion in an atomic species, leading to “cavityless” lasing. Lasing occurs from the population inversion that is created in the focal volume of...provide a reference that is capable of removing these pulse-to- pulse variations, a second, simultaneous backward lasing beam is generated using the same

Reconfigurable Solid-state Dye-doped Polymer Ring Resonator Lasers

NASA Astrophysics Data System (ADS)

Chandrahalim, Hengky; Fan, Xudong

2015-12-01

This paper presents wavelength configurable on-chip solid-state ring lasers fabricated by a single-mask standard lithography. The single- and coupled-ring resonator hosts were fabricated on a fused-silica wafer and filled with 3,3‧-Diethyloxacarbocyanine iodide (CY3), Rhodamine 6G (R6G), and 3,3‧-Diethylthiadicarbocyanine iodide (CY5)-doped polymer as the reconfigurable gain media. The recorded lasing threshold was ~220 nJ/mm2 per pulse for the single-ring resonator laser with R6G, marking the lowest threshold shown by solid-state dye-doped polymer lasers fabricated with a standard lithography process on a chip. A single-mode lasing from a coupled-ring resonator system with the lasing threshold of ~360 nJ/mm2 per pulse was also demonstrated through the Vernier effect. The renewability of the dye-doped polymer was examined by removing and redepositing the dye-doped polymer on the same resonator hosts for multiple cycles. We recorded consistent emissions from the devices for all trials, suggesting the feasibility of employing this technology for numerous photonic and biochemical sensing applications that entail for sustainable, reconfigurable, and low lasing threshold coherent light sources on a chip.

Reconfigurable Solid-state Dye-doped Polymer Ring Resonator Lasers

PubMed Central

Chandrahalim, Hengky; Fan, Xudong

2015-01-01

This paper presents wavelength configurable on-chip solid-state ring lasers fabricated by a single-mask standard lithography. The single- and coupled-ring resonator hosts were fabricated on a fused-silica wafer and filled with 3,3′-Diethyloxacarbocyanine iodide (CY3), Rhodamine 6G (R6G), and 3,3′-Diethylthiadicarbocyanine iodide (CY5)-doped polymer as the reconfigurable gain media. The recorded lasing threshold was ~220 nJ/mm2 per pulse for the single-ring resonator laser with R6G, marking the lowest threshold shown by solid-state dye-doped polymer lasers fabricated with a standard lithography process on a chip. A single-mode lasing from a coupled-ring resonator system with the lasing threshold of ~360 nJ/mm2 per pulse was also demonstrated through the Vernier effect. The renewability of the dye-doped polymer was examined by removing and redepositing the dye-doped polymer on the same resonator hosts for multiple cycles. We recorded consistent emissions from the devices for all trials, suggesting the feasibility of employing this technology for numerous photonic and biochemical sensing applications that entail for sustainable, reconfigurable, and low lasing threshold coherent light sources on a chip. PMID:26674508

Reconfigurable Solid-state Dye-doped Polymer Ring Resonator Lasers.

PubMed

Chandrahalim, Hengky; Fan, Xudong

2015-12-17

This paper presents wavelength configurable on-chip solid-state ring lasers fabricated by a single-mask standard lithography. The single- and coupled-ring resonator hosts were fabricated on a fused-silica wafer and filled with 3,3'-Diethyloxacarbocyanine iodide (CY3), Rhodamine 6G (R6G), and 3,3'-Diethylthiadicarbocyanine iodide (CY5)-doped polymer as the reconfigurable gain media. The recorded lasing threshold was ~220 nJ/mm(2) per pulse for the single-ring resonator laser with R6G, marking the lowest threshold shown by solid-state dye-doped polymer lasers fabricated with a standard lithography process on a chip. A single-mode lasing from a coupled-ring resonator system with the lasing threshold of ~360 nJ/mm(2) per pulse was also demonstrated through the Vernier effect. The renewability of the dye-doped polymer was examined by removing and redepositing the dye-doped polymer on the same resonator hosts for multiple cycles. We recorded consistent emissions from the devices for all trials, suggesting the feasibility of employing this technology for numerous photonic and biochemical sensing applications that entail for sustainable, reconfigurable, and low lasing threshold coherent light sources on a chip.

Optofluidic chlorophyll lasers.

PubMed

Chen, Yu-Cheng; Chen, Qiushu; Fan, Xudong

2016-06-21

Chlorophylls are essential for photosynthesis and also one of the most abundant pigments on earth. Using an optofluidic ring resonator of extremely high Q-factors (>10(7)), we investigated the unique characteristics and underlying mechanism of chlorophyll lasers. Chlorophyll lasers with dual lasing bands at 680 nm and 730 nm were observed for the first time in isolated chlorophyll a (Chla). Particularly, a laser at the 730 nm band was realized in 0.1 mM Chla with a lasing threshold of only 8 μJ mm(-2). Additionally, we observed lasing competition between the two lasing bands. The presence of laser emission at the 680 nm band can lead to quenching or significant reduction of laser emission at the 730 nm band, effectively increasing the lasing threshold for the 730 nm band. Further concentration-dependent studies, along with theoretical analysis, elucidated the mechanism that determines when and why the laser emission band appears at one of the two bands, or concomitantly at both bands. Finally, Chla was exploited as the donor in fluorescence resonance energy transfer to extend the laser emission to the near infrared regime with an unprecedented wavelength shift as large as 380 nm. Our work will open a door to the development of novel biocompatible and biodegradable chlorophyll-based lasers for various applications such as miniaturized tunable coherent light sources and in vitro/in vivo biosensing. It will also provide important insight into the chlorophyll fluorescence and photosynthesis processes inside plants.

Phase-locked laser array having a non-uniform spacing between lasing regions

NASA Technical Reports Server (NTRS)

Ackley, Donald E. (Inventor)

1986-01-01

A phase-locked semiconductor array wherein the lasing regions of the array are spaced an effective distance apart such that the modes of oscillation of the different lasing regions are phase-locked to one another. The center-to-center spacing between the lasing regions is non-uniform. This variation in spacing perturbs the preferred 180.degree. phase difference between adjacent lasing regions thereby providing an increased yield of arrays exhibiting a single-lobed, far-field radiation pattern.

Observation of random lasing in gold-silica nanoshell/water solution

NASA Astrophysics Data System (ADS)

Kang, Jin U.

2006-11-01

The author reports experimental observation of resonant surface plasmon enhanced random lasing in gold-silica nanoshells in de-ionized water. The gold-silica nanoshell/water solution with concentration of 8×109particles/ml was pumped above the surface plasmon resonance frequency using 514nm argon-krypton laser. When pumping power was above the lasing threshold, sharp random lasing peaks occurred near and below the plasmon peak from 720to860nm with a lasing linewidth less than 1nm.

1.55 μm room-temperature lasing from subwavelength quantum-dot microdisks directly grown on (001) Si

NASA Astrophysics Data System (ADS)

Shi, Bei; Zhu, Si; Li, Qiang; Tang, Chak Wah; Wan, Yating; Hu, Evelyn L.; Lau, Kei May

2017-03-01

Miniaturized laser sources can benefit a wide variety of applications ranging from on-chip optical communications and data processing, to biological sensing. There is a tremendous interest in integrating these lasers with rapidly advancing silicon photonics, aiming to provide the combined strength of the optoelectronic integrated circuits and existing large-volume, low-cost silicon-based manufacturing foundries. Using III-V quantum dots as the active medium has been proven to lower power consumption and improve device temperature stability. Here, we demonstrate room-temperature InAs/InAlGaAs quantum-dot subwavelength microdisk lasers epitaxially grown on (001) Si, with a lasing wavelength of 1563 nm, an ultralow-threshold of 2.73 μW, and lasing up to 60 °C under pulsed optical pumping. This result unambiguously offers a promising path towards large-scale integration of cost-effective and energy-efficient silicon-based long-wavelength lasers.

Self-photopumped x-ray lasers from elements in the Ne-like and Ni-like ionization state

DOE PAGES

Siegrist, Michael; Staub, Felix; Jia, Fei; ...

2016-08-11

In this paper, we report on experiments on the self-photopumped 3d 1P 1→3p 1P 1 and 4f 1P 1→4d 1P 1 laser transitions in Ne-like and Ni-like ions, respectively. Lasing on the self-photopumped laser line has been observed for the first time for a number of elements including Ne-like V, Cr, Fe, and Co as well as Ni-like Ru and Pd. We have investigated the lasing process by varying the prepulse delay, which shows a shift of the optimum main pulse to second prepulse delays towards lower values with higher atomic number Z. Time-resolved measurements showed that self-photopumped and monopolemore » collision-pumped lasing emission occurs essentially simultaneously. Finally, accurate wavelength measurements and calculations are shown to be in excellent agreement.« less

Brillouin lasing in single-mode tapered optical fiber with inscribed fiber Bragg grating array

NASA Astrophysics Data System (ADS)

Popov, S. M.; Butov, O. V.; Chamorovskiy, Y. K.; Isaev, V. A.; Kolosovskiy, A. O.; Voloshin, V. V.; Vorob'ev, I. L.; Vyatkin, M. Yu.; Mégret, P.; Odnoblyudov, M.; Korobko, D. A.; Zolotovskii, I. O.; Fotiadi, A. A.

2018-06-01

A tapered optical fiber has been manufactured with an array of fiber Bragg gratings (FBG) inscribed during the drawing process. The total fiber peak reflectivity is 5% and the reflection bandwidth is ∼3.5 nm. A coherent frequency domain reflectometry has been applied for precise profiling of the fiber core diameter and grating reflectivity both distributed along the whole fiber length. These measurements are in a good agreement with the specific features of Brillouin lasing achieved in the semi-open fiber cavity configuration.

Planar waveguide nanolaser configured by dye-doped hybrid nanofilm on substrate

NASA Astrophysics Data System (ADS)

Tikhonov, E. A.; Yashchuk, V. P.; Telbiz, G. M.

2018-04-01

Dye-doped hybrid silicate/titanium nanofilms on the glass substrate structures of asymmetrical waveguides were studied by way of laser systems. The threshold, spatial and spectral features of the laser oscillation of genuine and hollow waveguides were determined. The pattern of stimulated radiation included two concurrent processes: single-mode waveguide lasing and lateral small divergence emission. Comparison of the open angle of the lateral beams and grazing angles of the waveguide lasing mode provides an insight into the effect of leaky mode emission followed by Lummer-Gehrcke interference.

Phase-locked laser array

NASA Technical Reports Server (NTRS)

Botez, Dan (Inventor)

1987-01-01

A phase-locked laser array comprises a body of semiconductor material having means for defining a plurality of substantially parallel lasing zones which are spaced an effective distance apart so that the modes of the adjacent lasing zones are phase-locked to one another. One of the array electrodes comprises a plurality of electrical contacts to the body between the lasing zones. These contacts provide an enhanced current density profile and thus an increase in the gain in the regions between the lasing zones so that zero degree phase-shift operation between adjacent lasing zones is achievable.

Fission fragment excited laser system

DOEpatents

McArthur, David A.; Tollefsrud, Philip B.

1976-01-01

A laser system and method for exciting lasing action in a molecular gas lasing medium which includes cooling the lasing medium to a temperature below about 150 K and injecting fission fragments through the lasing medium so as to preferentially excite low lying vibrational levels of the medium and to cause population inversions therein. The cooled gas lasing medium should have a mass areal density of about 5 .times. 10.sup.-.sup.3 grams/square centimeter, relaxation times of greater than 50 microseconds, and a broad range of excitable vibrational levels which are excitable by molecular collisions.

Terahertz lasers and amplifiers based on resonant optical phonon scattering to achieve population inversion

NASA Technical Reports Server (NTRS)

Hu, Qing (Inventor); Williams, Benjamin S. (Inventor)

2007-01-01

The present invention provides quantum cascade lasers and amplifier that operate in a frequency range of about 1 Terahertz to about 10 Terahertz. In one aspect, a quantum cascade laser of the invention includes a semiconductor heterostructure that provides a plurality of lasing modules connected in series. Each lasing module includes a plurality of quantum well structure that collectively generate at least an upper lasing state, a lower lasing state, and a relaxation state such that the upper and the lower lasing states are separated by an energy corresponding to an optical frequency in a range of about 1 to about 10 Terahertz. The lower lasing state is selectively depopulated via resonant LO-phonon scattering of electrons into the relaxation state.

Terahertz lasers and amplifiers based on resonant optical phonon scattering to achieve population inversion

NASA Technical Reports Server (NTRS)

Williams, Benjamin S. (Inventor); Hu, Qing (Inventor)

2009-01-01

The present invention provides quantum cascade lasers and amplifier that operate in a frequency range of about 1 Terahertz to about 10 Terahertz. In one aspect, a quantum cascade laser of the invention includes a semiconductor heterostructure that provides a plurality of lasing modules connected in series. Each lasing module includes a plurality of quantum well structure that collectively generate at least an upper lasing state, a lower lasing state, and a relaxation state such that the upper and the lower lasing states are separated by an energy corresponding to an optical frequency in a range of about 1 to about 10 Terahertz. The lower lasing state is selectively depopulated via resonant LO-phonon scattering of electrons into the relaxation state.

Ultra-broad range organic solid-state laser from a dye-doped holographic grating quasi-waveguide configuration

NASA Astrophysics Data System (ADS)

Liu, Minghuan; Liu, Yonggang; Peng, Zenghui; Mu, Quanquan; Cao, Zhaoliang; Lu, Xinghai; Ma, Ji; Xuan, Li

2017-08-01

This paper reports the ultra-broad 149.1 nm lasing emission from 573.2 to 722.3 nm using a simple [4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran] (DCM)-doped holographic polymer-dispersed liquid crystal (HPDLC) grating quasi-waveguide configuration by varying the grating period. The lasing emission beams show s-polarization property. The quasi-waveguide structure, which contained the cover glass, the DCM-doped HPDLC grating, the semiconducting polymer film poly[-methoxy-5-(2‧-ethyl-hexyloxy)-1,4-phenylene-vinylene] (MEH-PPV), and the substrate were confirmed to decrease lasing threshold and broaden lasing wavelength. The operational lifetime of the device is 240 000 pulses, which corresponds to an overall laser duration of more than 6 h at a repetition rate of 10 Hz. In addition, the dual-wavelength lasing range from the 8th and 9th order is over 40 nm. The electrical tunability of the dual-wavelength lasing emission is over 1 nm. The experimental results facilitated the decreased lasing threshold and broadened lasing wavelength range of organic solid-state lasers.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slipchenko, S. O., E-mail: serghpl@mail.ioffe.ru; Podoskin, A. A.; Vinokurov, D. A.

Radiative characteristics of semiconductor stripe-contact lasers operating under quenching conditions of Fabry-Perot-mode lasing are studied. It is found that reversible turning off of Fabry-Perot-mode lasing is caused by switching to closed-mode lasing. Radiative characteristics of the closed mode are controlled by the mode structure with the close-to-zero loss for radiation output, which covers the entire crystal. The main threshold conditions of closed-mode lasing are a decrease in interband absorption in the passive region and an increase in the modal gain of the closed-mode lasing line. It is shown that a decrease in interband absorption in the passive region can bemore » provided by both spontaneous emission from the injection region and lasing-mode photons. An increase in the modal gain of the closed-mode lasing line is provided by shifting the energy minima of the conduction band and maxima of the valence band of the injection region with respect to the energy bands of the passive region.« less

Plasmon coupled Fabry-Perot lasing enhancement in graphene/ZnO hybrid microcavity.

PubMed

Li, Jitao; Jiang, Mingming; Xu, Chunxiang; Wang, Yueyue; Lin, Yi; Lu, Junfeng; Shi, Zengliang

2015-03-19

The response of graphene surface plasmon (SP) in the ultraviolet (UV) region and the realization of short-wavelength semiconductor lasers not only are two hot research areas of great academic and practical significance, but also are two important issues lacked of good understanding. In this work, a hybrid Fabry-Perot (F-P) microcavity, comprising of monolayer graphene covered ZnO microbelt, was constructed to investigate the fundamental physics of graphene SP and the functional extension of ZnO UV lasing. Through the coupling between graphene SP modes and conventional optical microcavity modes of ZnO, improved F-P lasing performance was realized, including the lowered lasing threshold, the improved lasing quality and the remarkably enhanced lasing intensity. The underlying mechanism of the improved lasing performance was proposed based on theoretical simulation and experimental characterization. The results are helpful to design new types of optic and photoelectronic devices based on SP coupling in graphene/semiconductor hybrid structures.

Plasmon coupled Fabry-Perot lasing enhancement in graphene/ZnO hybrid microcavity

PubMed Central

Li, Jitao; Jiang, Mingming; Xu, Chunxiang; Wang, Yueyue; Lin, Yi; Lu, Junfeng; Shi, Zengliang

2015-01-01

The response of graphene surface plasmon (SP) in the ultraviolet (UV) region and the realization of short-wavelength semiconductor lasers not only are two hot research areas of great academic and practical significance, but also are two important issues lacked of good understanding. In this work, a hybrid Fabry-Perot (F-P) microcavity, comprising of monolayer graphene covered ZnO microbelt, was constructed to investigate the fundamental physics of graphene SP and the functional extension of ZnO UV lasing. Through the coupling between graphene SP modes and conventional optical microcavity modes of ZnO, improved F-P lasing performance was realized, including the lowered lasing threshold, the improved lasing quality and the remarkably enhanced lasing intensity. The underlying mechanism of the improved lasing performance was proposed based on theoretical simulation and experimental characterization. The results are helpful to design new types of optic and photoelectronic devices based on SP coupling in graphene/semiconductor hybrid structures. PMID:25786359

Dual-lasing channel quantum cascade laser based on scattering-assisted injection design.

PubMed

Wen, Boyu; Xu, Chao; Wang, Siyi; Wang, Kaixi; Tam, Man Chun; Wasilewski, Zbig; Ban, Dayan

2018-04-02

A dual lasing channel Terahertz Quantum Cascade laser (THz QCL) based on GaAs/Al 0.17 Ga 0.83 As material system is demonstrated. The device shows the lowest reported threshold current density (550A/cm 2 at 50K) of GaAs/Al x Ga 1-x As material system based scattering-assisted (SA) structures and operates up to a maximum lasing temperature of 144K. Dual lasing channel operation is investigated theoretically and experimentally. The combination of low frequency emission, dual lasing channel operation, low lasing threshold current density and high temperature performance make such devices ideal candidates for low frequency applications, and initiates the design strategy for achieving high-temperature performance terahertz quantum cascade laser with wide frequency coverage at low frequency.

Tunable random lasing behavior in plasmonic nanostructures

NASA Astrophysics Data System (ADS)

Yadav, Ashish; Zhong, Liubiao; Sun, Jun; Jiang, Lin; Cheng, Gary J.; Chi, Lifeng

2017-01-01

Random lasing is desired in plasmonics nanostructures through surface plasmon amplification. In this study, tunable random lasing behavior was observed in dye molecules attached with Au nanorods (NRs), Au nanoparticles (NPs) and Au@Ag nanorods (NRs) respectively. Our experimental investigations showed that all nanostructures i.e., Au@AgNRs, AuNRs & AuNPs have intensive tunable spectral effects. The random lasing has been observed at excitation wavelength 532 nm and varying pump powers. The best random lasing properties were noticed in Au@AgNRs structure, which exhibits broad absorption spectrum, sufficiently overlapping with that of dye Rhodamine B (RhB). Au@AgNRs significantly enhance the tunable spectral behavior through localized electromagnetic field and scattering. The random lasing in Au@AgNRs provides an efficient coherent feedback for random lasers.

Lasing in chiral photonic liquid crystals and associated frequency tuning.

PubMed

Fuh, Andy; Lin, Tsung-Hsien; Liu, J-H; Wu, F-C

2004-05-03

This letter addresses a dye-doped planar cholesteric cell as a one-dimensional photonic crystal, which can be lased at the band edges of the photonic band gap. The effect of the composition of the material and the thickness of a cholesteric cell (CLC) on the lasing action, and the photo-control of the lasing frequency, are experimentally investigated. Adding a tunable chiral monomer (TCM) allows the CLC's reflection band to be tuned by varying the intensity and/or exposure time of the UV curing light, enabling the lasing frequency of the CLC sample to be tuned.

Can the KTP laser change the cementum surface of healthy and diseased teeth providing an acceptable root surface for fibroblast attachment?

NASA Astrophysics Data System (ADS)

Mailhot, Jason M.; Garnick, Jerry J.

1996-04-01

The purpose of our research is to determine the effects of KTP laser on root cementum and fibroblast attachment. Initial work has been completed in testing the effect of different energy levels on root surfaces. From these studies optimal energy levels were determined. In subsequent studies the working distance and exposure time required to obtain significant fibroblast attachment to healthy cementum surfaces were investigated. Results showed that lased cemental surfaces exhibited changes in surface topography which ranged from a melted surface to an apparent slight fusion of the surface of the covering smear layer. When the optimal energy level was used, fibroblasts demonstrate attachment on the specimens, resulting in the presence of a monolayer of cells on the control surfaces as well as on the surfaces lased with this energy level. The present study investigates the treatment of pathological root surfaces and calculus with a KTP laser utilizing these optimal parameters determine previously. Thirty single rooted teeth with advanced periodontal disease and ten healthy teeth were obtained, crowns were sectioned and roots split longitudinally. Forty test specimens were assigned into 1 of 4 groups; pathologic root--not lased, pathologic root--lased, root planed root and health root planed root. Human gingival fibroblasts were seeded on specimens and cultured for 24 hours. Specimens were processed for SEM. The findings suggest that with the KTP laser using a predetermined energy level applied to pathological root surfaces, the lased surfaces provided an unacceptable surface for fibroblast attachment. However, the procedural control using healthy root planed surfaces did demonstrate fibroblast attachment.

Bose Condensation and Lasing in Optical Microstructures - Part 1

NASA Astrophysics Data System (ADS)

Szymanska, M. H.

2002-04-01

In the first part of this thesis I study the intermediate regime between ordinary lasing and a BEC of exciton polaritons. I take into account the fermionic structure of polaritons, treating the excitons as two-level systems coupled to a single mode in a microcavity. I introduce decoherence and dissipation processes to this system. Employing many-body Green function techniques, similar to those used by Abrikosov and Gor'kov in their theory of gapless superconductivity, I provide a mathematical structure that unifies models of lasers with models of condensates. This allows me to study the stability of the polariton condensate with respect to decoherence processes and the crossover between the polariton condensate and the laser. I give detailed indications of a regime in which the condensate should be observed to guide experimental work and show how to distinguish the Bose condensate from a laser. The second part of this thesis is concerned with properties of excitons and modelling of excitonic lasing in quasi-one-dimensional quantum wires. I develop a very general numerical method of calculating the properties of wires with different shapes and materials. Using this method I study the properties of very wide range of T-shaped quantum wires.

LASE measurements of water vapor, aerosol, and cloud distribution in hurricane environments and their role in hurricane development

NASA Technical Reports Server (NTRS)

Mahoney, M. J.; Ismail, S.; Browell, E. V.; Ferrare, R. A.; Kooi, S. A.; Brasseur, L.; Notari, A.; Petway, L.; Brackett, V.; Clayton, M.;

Gas laser with dual plasma mixing

DOEpatents

Pinnaduwage, L.A.

1999-04-06

A gas laser includes an enclosure forming a first chamber, a second chamber and a lasing chamber which communicates through a first opening to the first chamber and through a second opening to the second chamber. The lasing chamber has a pair of reflectors defining a Fabry-Perot cavity. Separate inlets enable different gases to be introduced into the first and second chambers. A first cathode within the first chamber is provided to produce positive ions which travel into the lasing chamber and a second cathode of a pin-hollow type within the second chamber is provided to produce negative ions which travel into the lasing chamber. A third inlet introduces a molecular gas into the lasing chamber, where the molecular gas becomes excited by the positive and negative ions and emits light which lases in the Fabry-Perot cavity. 2 figs.

Gas laser with dual plasma mixing

DOEpatents

Pinnaduwage, Lal A.

1999-01-01

A gas laser includes an enclosure forming a first chamber, a second chamber and a lasing chamber which communicates through a first opening to the first chamber and through a second opening to the second chamber. The lasing chamber has a pair of reflectors defining a Fabry-Perot cavity. Separate inlets enable different gases to be introduced into the first and second chambers. A first cathode within the first chamber is provided to produce positive ions which travel into the lasing chamber and a second cathode of a pin-hollow type within the second chamber is provided to produce negative ions which travel into the lasing chamber. A third inlet introduces a molecular gas into the lasing chamber, where the molecular gas becomes excited by the positive and negative ions and emits light which lases in the Fabry-Perot cavity.

Flexible random lasers with tunable lasing emissions.

PubMed

Lee, Ya-Ju; Chou, Chun-Yang; Yang, Zu-Po; Nguyen, Thi Bich Hanh; Yao, Yung-Chi; Yeh, Ting-Wei; Tsai, Meng-Tsan; Kuo, Hao-Chun

2018-04-19

In this study, we experimentally demonstrated a flexible random laser fabricated on a polyethylene terephthalate (PET) substrate with a high degree of tunability in lasing emissions. Random lasing oscillation arises mainly from the resonance coupling between the emitted photons of gain medium (Rhodamine 6G, R6G) and the localized surface plasmon (LSP) of silver nanoprisms (Ag NPRs), which increases the effective cross-section for multiple light scattering, thus stimulating the lasing emissions. More importantly, it was found that the random lasing wavelength is blue-shifted monolithically with the increase in bending strains exerted on the PET substrate, and a maximum shift of ∼15 nm was achieved in the lasing wavelength, when a 50% bending strain was exerted on the PET substrate. Such observation is highly repeatable and reversible, and this validates that we can control the lasing wavelength by simply bending the flexible substrate decorated with the Ag NPRs. The scattering spectrum of the Ag NPRs was obtained using a dark-field microscope to understand the mechanism for the dependence of the wavelength shift on the exerted bending strains. As a result, we believe that the experimental demonstration of tunable lasing emissions based on the revealed structure is expected to open up a new application field of random lasers.

Optimizing the 391-nm lasing intensity from ionized nitrogen molecules in 800-nm femtosecond laser fields

NASA Astrophysics Data System (ADS)

Zhong, Xunqi; Miao, Zhiming; Zhang, Linlin; Jiang, Hongbing; Liu, Yunquan; Gong, Qihuang; Wu, Chengyin

2018-03-01

We investigate the 391-nm lasing dynamics from ionized nitrogen molecules in 800-nm femtosecond laser fields. By comparing the radiation intensity, spectrum shape, and temporal profile of the 391-nm lasing at various experimental conditions, we conclude that the lasing dynamics contains not only the generation and the decay of ionized nitrogen molecules, but also the seed-built coherence among emitters as well as the propagation effect in the plasma filamentation. These results provide reliable guidance for optimizing the 391-nm lasing from ionized nitrogen molecules in 800-nm femtosecond laser fields, which have potential applications for remote sensing in the atmosphere.

Cascaded Brillouin lasing in monolithic barium fluoride whispering gallery mode resonators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Guoping, E-mail: guoping.lin@femto-st.fr; Diallo, Souleymane; Saleh, Khaldoun

2014-12-08

We report the observation of stimulated Brillouin scattering and lasing at 1550 nm in barium fluoride (BaF{sub 2}) crystal. Brillouin lasing was achieved with ultra-high quality (Q) factor monolithic whispering gallery mode mm-size disk resonators. Overmoded resonators were specifically used to provide cavity resonances for both the pump and all Brillouin Stokes waves. Single and multiple Brillouin Stokes radiations with frequency shift ranging from 8.2 GHz up to 49 GHz have been generated through cascaded Brillouin lasing. BaF{sub 2} resonator-based Brillouin lasing can find potential applications for high-coherence lasers and microwave photonics.

Hybrid Multilayered Plasmonic Nanostars for Coherent Random Lasing.

PubMed

Munkhbat, Battulga; Ziegler, Johannes; Pöhl, Hannes; Wörister, Christian; Sivun, Dmitry; Scharber, Markus C; Klar, Thomas A; Hrelescu, Calin

2016-10-20

Here, we report that hybrid multilayered plasmonic nanostars can be universally used as feedback agents for coherent random lasing in polar or nonpolar solutions containing gain material. We show that silver-enhancement of gold nanostars reduces the pumping threshold for coherent random lasing substantially for both a typical dye (R6G) and a typical fluorescent polymer (MEH-PPV). Further, we reveal that the lasing intensity and pumping threshold of random lasers based on silver-enhanced gold nanostars are not influenced by the silica coating, in contrast to gold nanostar-based random lasers, where silica-coated gold nanostars support only amplified spontaneous emission but no coherent random lasing.

CO.sub.2 laser

DOEpatents

Rink, John P.

1977-01-01

The disclosure relates to a pulsed gas laser comprising an optical resonant cavity, a CO.sub.2 lasing medium, structure for containing the CO.sub.2 lasing medium within the optical cavity and a device for causing a population inversion in the lasing medium, with a novel improvement comprising structure for causing a laser pulse comprising a wavelength in the near 14 .mu.m and near 16 .mu.m range. The structure for cooling the CO.sub.2 lasing medium to less than about -40.degree. C as well is a structure for pumping the maximum inversion of CO.sub.2 molecules within the lasing medium by minimizing the population in the 010 level.

Development of the Lidar Atmospheric Sensing Experiment (LASE): An Advanced Airborne DIAL Instrument

NASA Technical Reports Server (NTRS)

Moore, Alvah S., Jr.; Brown, Kevin E.; Hall, William M.; Barnes, James C.; Edwards, William C.; Petway, Larry B.; Little, Alan D.; Luck, William S., Jr.; Jones, Irby W.; Antill, Charles W., Jr.

1997-01-01

The Lidar Atmospheric Sensing Experiment (LASE) Instrument is the first fully-engineered, autonomous Differential Absorption Lidar (DIAL) System for the measurement of water vapor in the troposphere (aerosol and cloud measurements are included). LASE uses a double-pulsed Ti:Sapphire laser for the transmitter with a 30 ns pulse length and 150 mJ/pulse. The laser beam is "seeded" to operate on a selected water vapor absorption line in the 815-nm region using a laser diode and an onboard absorption reference cell. A 40 cm diameter telescope collects the backscattered signals and directs them onto two detectors. LASE collects DIAL data at 5 Hz while onboard a NASA/Ames ER-2 aircraft flying at altitudes from 16-21 km. LASE was designed to operate autonomously within the environment and physical constraints of the ER-2 aircraft and to make water vapor profile measurements across the troposphere to better than 10% accuracy. LASE has flown 19 times during the development of the instrument and the validation of the science data. This paper describes the design, operation, and reliability of the LASE Instrument.

Characterization of Upper Troposphere Water Vapor Measurements during AFWEX using LASE

NASA Technical Reports Server (NTRS)

Ferrare, R. A.; Browell, E. V.; Ismail, S.; Kooi, S.; Brasseur, L. H.; Brackett, V. G.; Clayton, M.; Barrick, J.; Linne, H.; Lammert, A.

2002-01-01

Water vapor profiles from NASA's Lidar Atmospheric Sensing Experiment (LASE) system acquired during the ARM/FIRE Water Vapor Experiment (AFWEX) are used to characterize upper troposphere water vapor (UTWV) measured by ground-based Raman lidars, radiosondes, and in situ aircraft sensors. Initial comparisons showed the average Vaisala radiosonde measurements to be 5-15% drier than the average LASE, Raman lidar, and DC-8 in situ diode laser hygrometer measurements. We show that corrections to the Raman lidar and Vaisala measurements significantly reduce these differences. Precipitable water vapor (PWV) derived from the LASE water vapor profiles agrees within 3% on average with PWV derived from the ARM ground-based microwave radiometer (MWR). The agreement among the LASE, Raman lidar, and MWR measurements demonstrates how the LASE measurements can be used to characterize both profile and column water vapor measurements and that ARM Raman lidar, when calibrated using the MWR PWV, can provide accurate UTWV measurements.

Lasing in silicon–organic hybrid waveguides

PubMed Central

Korn, Dietmar; Lauermann, Matthias; Koeber, Sebastian; Appel, Patrick; Alloatti, Luca; Palmer, Robert; Dumon, Pieter; Freude, Wolfgang; Leuthold, Juerg; Koos, Christian

2016-01-01

Silicon photonics enables large-scale photonic–electronic integration by leveraging highly developed fabrication processes from the microelectronics industry. However, while a rich portfolio of devices has already been demonstrated on the silicon platform, on-chip light sources still remain a key challenge since the indirect bandgap of the material inhibits efficient photon emission and thus impedes lasing. Here we demonstrate a class of infrared lasers that can be fabricated on the silicon-on-insulator (SOI) integration platform. The lasers are based on the silicon–organic hybrid (SOH) integration concept and combine nanophotonic SOI waveguides with dye-doped organic cladding materials that provide optical gain. We demonstrate pulsed room-temperature lasing with on-chip peak output powers of up to 1.1 W at a wavelength of 1,310 nm. The SOH approach enables efficient mass-production of silicon photonic light sources emitting in the near infrared and offers the possibility of tuning the emission wavelength over a wide range by proper choice of dye materials and resonator geometry. PMID:26949229

Tunable liquid-crystal microshell-laser based on whispering-gallery modes and photonic band-gap mode lasing.

PubMed

Lu, Yuelan; Yang, Yue; Wang, Yan; Wang, Lei; Ma, Ji; Zhang, Lingli; Sun, Weimin; Liu, Yongjun

2018-02-05

The lasing behaviors of dye-doped cholesteric liquid crystal (DDCLC) microshells fabricated with silica-glass-microsphere coated DDCLCs were examined. Lasing characteristics were studied in a carrier medium with different refractive indices. The lasing in spherical cholesteric liquid crystals (CLCs) was attributed to two mechanisms, photonic band-gap (PBG) lasing and whispering-gallery modes (WGMs), which can independently exist by varying the chiral agent concentration and pumping energy. It was also found that DDCLC microshells can function as highly sensitive thermal sensors, with a temperature sensitivity of 0.982 nm °C -1 in PBG modes and 0.156 nm °C -1 in WGMs.

The influence of p-doping on two-state lasing in InAs/InGaAs quantum dot lasers

NASA Astrophysics Data System (ADS)

Maximov, M. V.; Shernyakov, Yu M.; Zubov, F. I.; Zhukov, A. E.; Gordeev, N. Yu; Korenev, V. V.; Savelyev, A. V.; Livshits, D. A.

2013-10-01

Two-state lasing in devices based on undoped and p-type modulation-doped InAs/InGaAs quantum dots is studied for various cavity lengths and temperatures. Modulation doping of the active region strongly enhances the threshold current of two-state lasing, preserves ground-state lasing up to higher temperatures and increases ground-state output power. The impact of modulation doping is especially strong in short cavities.

Continuous two-wave lasing in microchip Nd : YAG lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ievlev, Ivan V; Koryukin, Igor' V; Lebedeva, Yu S

2011-08-31

Simultaneous two-wave lasing was obtained in microchip end-pumped Nd:YAG lasers at the wavelengths of 1061.5 and 1064.17 nm at room temperature. Laser wave intensities were studied as functions of crystal temperature and pump power. The ranges of parameters were determined in which the two-wave lasing occurs and the reasons for such lasing were established. A model is suggested, which adequately describes the experimental results obtained. (control of radiation parameters)

Thermal effects in Cs DPAL and alkali cell window damage

NASA Astrophysics Data System (ADS)

Zhdanov, B. V.; Rotondaro, M. D.; Shaffer, M. K.; Knize, R. J.

2016-10-01

Experiments on power scaling of Diode Pumped Alkali Lasers (DPALs) revealed some limiting parasitic effects such as alkali cell windows and gain medium contamination and damage, output power degradation in time and others causing lasing efficiency decrease or even stop lasing1 . These problems can be connected with thermal effects, ionization, chemical interactions between the gain medium components and alkali cells materials. Study of all these and, possibly, other limiting effects and ways to mitigate them is very important for high power DPAL development. In this talk we present results of our experiments on temperature measurements in the gain medium of operating Cs DPAL at different pump power levels in the range from lasing threshold to the levels causing damage of the alkali cell windows. For precise contactless in situ temperature measurements, we used an interferometric technique, developed in our lab2 . In these experiments we demonstrated that damage of the lasing alkali cell starts in the bulk with thermal breakdown of the hydrocarbon buffer gas. The degradation processes start at definite critical temperatures of the gain medium, different for each mixture of buffer gas. At this critical temperature, the hydrocarbon and the excited alkali metal begin to react producing the characteristic black soot and, possibly, some other chemical compounds, which both harm the laser performance and significantly increase the harmful heat deposition within the laser medium. This soot, being highly absorptive, is catastrophically heated to very high temperatures that visually observed as bulk burning. This process quickly spreads to the cell windows and causes their damage. As a result, the whole cell is also contaminated with products of chemical reactions.

Weak lasing in one-dimensional polariton superlattices.

PubMed

Zhang, Long; Xie, Wei; Wang, Jian; Poddubny, Alexander; Lu, Jian; Wang, Yinglei; Gu, Jie; Liu, Wenhui; Xu, Dan; Shen, Xuechu; Rubo, Yuri G; Altshuler, Boris L; Kavokin, Alexey V; Chen, Zhanghai

2015-03-31

Bosons with finite lifetime exhibit condensation and lasing when their influx exceeds the lasing threshold determined by the dissipative losses. In general, different one-particle states decay differently, and the bosons are usually assumed to condense in the state with the longest lifetime. Interaction between the bosons partially neglected by such an assumption can smear the lasing threshold into a threshold domain--a stable lasing many-body state exists within certain intervals of the bosonic influxes. This recently described weak lasing regime is formed by the spontaneously symmetry breaking and phase-locking self-organization of bosonic modes, which results in an essentially many-body state with a stable balance between gains and losses. Here we report, to our knowledge, the first observation of the weak lasing phase in a one-dimensional condensate of exciton-polaritons subject to a periodic potential. Real and reciprocal space photoluminescence images demonstrate that the spatial period of the condensate is twice as large as the period of the underlying periodic potential. These experiments are realized at room temperature in a ZnO microwire deposited on a silicon grating. The period doubling takes place at a critical pumping power, whereas at a lower power polariton emission images have the same periodicity as the grating.

Lasing of a Solid-State Active Element Based on Anodized Aluminum Oxide Film Doped with Rhodamine 6G

NASA Astrophysics Data System (ADS)

Shelkovnikov, V. V.; Lyubas, G. A.; Korotaev, S. V.; Kopylova, T. N.; Tel'minov, E. N.; Gadirov, R. M.; Nikonova, E. N.; Nikonov, S. Yu.; Solodova, T. A.; Novikov, V. A.

2017-04-01

Spectral-luminescent and lasing characteristics of rhodamine 6G in porous aluminum oxide films anodized under various conditions are investigated. Lasing is obtained without external resonator in the longitudinal scheme under excitation by the second harmonic of Nd3+:YAG-laser radiation. The threshold pump power densities are in the range 3.5-15 MW/cm2 depending on the anodizing conditions. Wherein, the lasing line narrows down from 12 to 5 nm.

Random lasing in dye-doped polymer dispersed liquid crystal film

NASA Astrophysics Data System (ADS)

Wu, Rina; Shi, Rui-xin; Wu, Xiaojiao; Wu, Jie; Dai, Qin

2016-09-01

A dye-doped polymer-dispersed liquid crystal film was designed and fabricated, and random lasing action was studied. A mixture of laser dye, nematic liquid crystal, chiral dopant, and PVA was used to prepare the dye-doped polymer-dispersed liquid crystal film by means of microcapsules. Scanning electron microscopy analysis showed that most liquid crystal droplets in the polymer matrix ranged from 30 μm to 40 μm, the size of the liquid crystal droplets was small. Under frequency doubled 532 nm Nd:YAG laser-pumped optical excitation, a plurality of discrete and sharp random laser radiation peaks could be measured in the range of 575-590 nm. The line-width of the lasing peak was 0.2 nm and the threshold of the random lasing was 9 mJ. Under heating, the emission peaks of random lasing disappeared. By detecting the emission light spot energy distribution, the mechanism of radiation was found to be random lasing. The random lasing radiation mechanism was then analyzed and discussed. Experimental results indicated that the size of the liquid crystal droplets is the decisive factor that influences the lasing mechanism. The surface anchor role can be ignored when the size of the liquid crystal droplets in the polymer matrix is small, which is beneficial to form multiple scattering. The transmission path of photons is similar to that in a ring cavity, providing feedback to obtain random lasing output. Project supported by the National Natural Science Foundation of China (Grant No. 61378042), the Colleges and Universities in Liaoning Province Outstanding Young Scholars Growth Plans, China (Grant No. LJQ2015093), and Shenyang Ligong University Laser and Optical Information of Liaoning Province Key Laboratory Open Funds, China.

Enhanced Exciton and Photon Confinement in Ruddlesden-Popper Perovskite Microplatelets for Highly Stable Low-Threshold Polarized Lasing.

PubMed

Li, Mingjie; Wei, Qi; Muduli, Subas Kumar; Yantara, Natalia; Xu, Qiang; Mathews, Nripan; Mhaisalkar, Subodh G; Xing, Guichuan; Sum, Tze Chien

2018-06-01

At the heart of electrically driven semiconductors lasers lies their gain medium that typically comprises epitaxially grown double heterostuctures or multiple quantum wells. The simultaneous spatial confinement of charge carriers and photons afforded by the smaller bandgaps and higher refractive index of the active layers as compared to the cladding layers in these structures is essential for the optical-gain enhancement favorable for device operation. Emulating these inorganic gain media, superb properties of highly stable low-threshold (as low as ≈8 µJ cm -2 ) linearly polarized lasing from solution-processed Ruddlesden-Popper (RP) perovskite microplatelets are realized. Detailed investigations using microarea transient spectroscopies together with finite-difference time-domain simulations validate that the mixed lower-dimensional RP perovskites (functioning as cladding layers) within the microplatelets provide both enhanced exciton and photon confinement for the higher-dimensional RP perovskites (functioning as the active gain media). Furthermore, structure-lasing-threshold relationship (i.e., correlating the content of lower-dimensional RP perovskites in a single microplatelet) vital for design and performance optimization is established. Dual-wavelength lasing from these quasi-2D RP perovskite microplatelets can also be achieved. These unique properties distinguish RP perovskite microplatelets as a new family of self-assembled multilayer planar waveguide gain media favorable for developing efficient lasers. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The excitonic photoluminescence mechanism and lasing action in band-gap-tunable CdS(1-x)Se(x) nanostructures.

PubMed

Dai, Jun; Zhou, Pengxia; Lu, Junfeng; Zheng, Hongge; Guo, Jiyuan; Wang, Fang; Gu, Ning; Xu, Chunxiang

2016-01-14

Bandgap tunable semiconductor materials have wide application in integrated-optoelectronic and communication devices. The CdS1-xSex ternary semiconductor materials covering green-red bands have been reported previously, but their basic band-gap and optical properties crucial to the performance of the CdS1-xSex-based optoelectronic devices have not been deeply understood. In this paper, we theoretically simulated and discussed the feasibility of bandgap-tunable CdS1-xSex nanomaterials for designing wavelength tunable microlasers. Then we fabricated the CdS1-xSex nanobelts with their band gap ranging from 2.4 to 1.74 eV by adjusting the composition ratio x in the vapor-phase-transport growth process. The temperature-dependent photoluminescence and exciton-related optical constants of the CdS1-xSex nanobelts were carefully demonstrated. Finally, the wavelength-tunable Fabry-Perot lasing in CdS1-xSex nanobelts was obtained, and the Fabry-Perot lasing mechanism was numerically simulated by the FDTD method. The systematic results on the mechanism of the tunable band gap, exciton properties and lasing of the CdS1-xSex nanostructure help us deeply understand the intrinsic optical properties of this material, and will build a strong foundation for future application of green-red wavelength-tunable CdS1-xSex microlasers.

Photoinduced charge carriers' accumulation and its impact on random lasing in Nd3+ doped (Pb,La)(Zr,Ti)O3 ceramics

NASA Astrophysics Data System (ADS)

Xu, Caixia; Zhang, Jingwen; Xu, Long; Ma, Xinyan; Zhao, Hua

2017-06-01

To pinpoint the driving forces behind the random lasing in Nd3+ doped lanthanum lead zirconate titanate (Nd:PLZT) ceramic plates, a combinatorial cavity with two gain media (Nd:YVO4 and Nd:PLZT) was used to study the switching feature between conventional lasing and random lasing oscillations. The complex laser output dynamics observed hinted that the photo-induced charge accumulation on the plate surface and the grain boundaries of Nd:PLZT is responsible for the lasing action switching, which was confirmed by a series of experiments, including strong electro-induced scattering, remarkable photoinduced currents, and light transmission reduction, along with measured single-pass-gain over the theoretical limit. It was found that the charge accumulation results in optical energy storage and nonuniform refractive index and hence strong scattering, which give rise to the random walks and weak localization of photons and long lasting lasing action and mode switching.

Lasing in a three-dimensional photonic crystal of the liquid crystal blue phase II.

PubMed

Cao, Wenyi; Muñoz, Antonio; Palffy-Muhoray, Peter; Taheri, Bahman

2002-10-01

Photonic-bandgap materials, with periodicity in one, two or three dimensions, offer control of spontaneous emission and photon localization. Low-threshold lasing has been demonstrated in two-dimensional photonic-bandgap materials, both with distributed feedback and defect modes. Liquid crystals with chiral constituents exhibit mesophases with modulated ground states. Helical cholesterics are one-dimensional, whereas blue phases are three-dimensional self-assembled photonic-bandgap structures. Although mirrorless lasing was predicted and observed in one-dimensional helical cholesteric materials and chiral ferroelectric smectic materials, it is of great interest to probe light confinement in three dimensions. Here, we report the first observations of lasing in three-dimensional photonic crystals, in the cholesteric blue phase II. Our results show that distributed feedback is realized in three dimensions, resulting in almost diffraction-limited lasing with significantly lower thresholds than in one dimension. In addition to mirrorless lasing, these self-assembled soft photonic-bandgap materials may also be useful for waveguiding, switching and sensing applications.

Single Mode ZnO Whispering-Gallery Submicron Cavity and Graphene Improved Lasing Performance.

PubMed

Li, Jitao; Lin, Yi; Lu, Junfeng; Xu, Chunxiang; Wang, Yueyue; Shi, Zengliang; Dai, Jun

2015-07-28

Single-mode ultraviolet (UV) laser of ZnO is still in challenge so far, although it has been paid great attention along the past decades. In this work, single-mode lasing resonance was realized in a submicron-sized ZnO rod based on serially varying the dimension of the whispering-gallery mode (WGM) cavities. The lasing performance, such as the lasing quality factor (Q) and the lasing intensity, was remarkably improved by facilely covering monolayer graphene on the ZnO submicron-rod. The mode structure evolution from multimodes to single-mode was investigated systematically based on the total internal-wall reflection of the ZnO microcavities. Graphene-induced optical field confinement and lasing emission enhancement were revealed, indicating an energy coupling between graphene SP and ZnO exciton emission. This result demonstrated the response of graphene in the UV wavelength region and extended its potential applications besides many previous reports on the multifunctional graphene/semiconductor hybrid materials and devices in advanced electronics and optoelectronics areas.

Characterization of upper troposphere water vapor measurements during AFWEX using LASE.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferrare, R. A.; Browell, E. V.; Ismail, I.

2002-07-15

Water vapor profiles from NASA's Lidar Atmospheric Sensing Experiment (LASE) system acquired during the ARM/FIRE Water Vapor Experiment (AFWEX) are used to characterize upper troposphere (UT) water vapor measured by ground-based Raman lidars, radiosondes, and in situ aircraft sensors. Initial comparisons showed the average Vaisala radiosonde measurements to be 5-15% drier than the average LASE, Raman lidar, and DC-8 in situ diode laser hygrometer measurements. They show that corrections to the Raman lidar and Vaisala measurements significantly reduce these differences. Precipitable water vapor (PWV) derived from the LASE water vapor profiles agrees within 3% on average with PWV derived frommore » the ARM ground-based microwave radiometer (MWR). The agreement among the LASE, Raman lidar, and MWR measurements demonstrates how the LASE measurements can be used to characterize both profile and column water vapor measurements and that ARM Raman lidar, when calibrated using the MWR PWV, can provide accurate UT water vapor measurements.« less

Nanowire–quantum-dot lasers on flexible membranes

NASA Astrophysics Data System (ADS)

Tatebayashi, Jun; Ota, Yasutomo; Ishida, Satomi; Nishioka, Masao; Iwamoto, Satoshi; Arakawa, Yasuhiko

2018-06-01

We demonstrate lasing in a single nanowire with quantum dots as an active medium embedded on poly(dimethylsiloxane) membranes towards application in nanowire-based flexible nanophotonic devices. Nanowire laser structures with 50 quantum dots are grown on patterned GaAs(111)B substrates and then transferred from the as-grown substrates on poly(dimethylsiloxane) transparent flexible organosilicon membranes, by means of spin-casting and curing processes. We observe lasing oscillation in the transferred single nanowire cavity with quantum dots at 1.425 eV with a threshold pump pulse fluence of ∼876 µJ/cm2, which enables the realization of high-performance multifunctional NW-based flexible photonic devices.

Laser power transmission

NASA Technical Reports Server (NTRS)

Conway, Edmund J.

1992-01-01

An overview of previous studies related to laser power transmission is presented. Particular attention is given to the use of solar pumped lasers for space power applications. Three general laser mechanisms are addressed: photodissociation lasing driven by sunlight, photoexcitation lasing driven directly by sunlight, and photoexcitation lasing driven by thermal radiation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baek, Hyeonjun; Hyun, Jerome K.; Chung, Kunook

Lasing from long semiconductor nanorods is dictated by Fabry-Perot (FP) resonances whereas that from large-diameter microrods is determined by whispering gallery modes (WGMs). Lengths and diameters intermediate between the two systems represent an important size regime for photonics and electronics, but have not been studied in detail. Here, we report on the detection of FP and WGM lasing emissions from a single GaN microrod, and demonstrate the ability to switch between the two lasing mechanisms by translating the excitation beam along the microrod. The competition between FP and WGM-type lasing was studied by finite-difference time-domain simulation and statistical analysis bymore » measuring microrods of various diameters. Finally, control over the relative lasing intensities originating from either FPs or WGMs was demonstrated by tuning the polarization of the emission.« less

Weak lasing in one-dimensional polariton superlattices

PubMed Central

Zhang, Long; Xie, Wei; Wang, Jian; Poddubny, Alexander; Lu, Jian; Wang, Yinglei; Gu, Jie; Liu, Wenhui; Xu, Dan; Shen, Xuechu; Rubo, Yuri G.; Altshuler, Boris L.; Kavokin, Alexey V.; Chen, Zhanghai

2015-01-01

Bosons with finite lifetime exhibit condensation and lasing when their influx exceeds the lasing threshold determined by the dissipative losses. In general, different one-particle states decay differently, and the bosons are usually assumed to condense in the state with the longest lifetime. Interaction between the bosons partially neglected by such an assumption can smear the lasing threshold into a threshold domain—a stable lasing many-body state exists within certain intervals of the bosonic influxes. This recently described weak lasing regime is formed by the spontaneously symmetry breaking and phase-locking self-organization of bosonic modes, which results in an essentially many-body state with a stable balance between gains and losses. Here we report, to our knowledge, the first observation of the weak lasing phase in a one-dimensional condensate of exciton–polaritons subject to a periodic potential. Real and reciprocal space photoluminescence images demonstrate that the spatial period of the condensate is twice as large as the period of the underlying periodic potential. These experiments are realized at room temperature in a ZnO microwire deposited on a silicon grating. The period doubling takes place at a critical pumping power, whereas at a lower power polariton emission images have the same periodicity as the grating. PMID:25787253

Cross-talk free, low-noise optical amplifier

DOEpatents

Dijaili, Sol P.; Patterson, Frank G.; Deri, Robert J.

1995-01-01

A low-noise optical amplifier solves crosstalk problems in optical amplifiers by using an optical cavity oriented off-axis (e.g. perpendicular) to the direction of a signal amplified by the gain medium of the optical amplifier. Several devices are used to suppress parasitic lasing of these types of structures. The parasitic lasing causes the gain of these structures to be practically unusable. The lasing cavity is operated above threshold and the gain of the laser is clamped to overcome the losses of the cavity. Any increase in pumping causes the lasing power to increase. The clamping action of the gain greatly reduces crosstalk due to gain saturation for the amplified signal beam. It also reduces other nonlinearities associated with the gain medium such as four-wave mixing induced crosstalk. This clamping action can occur for a bandwidth defined by the speed of the laser cavity. The lasing field also reduces the response time of the gain medium. By having the lasing field off-axis, no special coatings are needed. Other advantages are that the lasing field is easily separated from the amplified signal and the carrier grating fluctuations induced by four-wave mixing are decreased. Two related methods reduce the amplified spontaneous emission power without sacrificing the gain of the optical amplifier.

Cross-talk free, low-noise optical amplifier

DOEpatents

Dijaili, S.P.; Patterson, F.G.; Deri, R.J.

1995-07-25

A low-noise optical amplifier solves crosstalk problems in optical amplifiers by using an optical cavity oriented off-axis (e.g. perpendicular) to the direction of a signal amplified by the gain medium of the optical amplifier. Several devices are used to suppress parasitic lasing of these types of structures. The parasitic lasing causes the gain of these structures to be practically unusable. The lasing cavity is operated above threshold and the gain of the laser is clamped to overcome the losses of the cavity. Any increase in pumping causes the lasing power to increase. The clamping action of the gain greatly reduces crosstalk due to gain saturation for the amplified signal beam. It also reduces other nonlinearities associated with the gain medium such as four-wave mixing induced crosstalk. This clamping action can occur for a bandwidth defined by the speed of the laser cavity. The lasing field also reduces the response time of the gain medium. By having the lasing field off-axis, no special coatings are needed. Other advantages are that the lasing field is easily separated from the amplified signal and the carrier grating fluctuations induced by four-wave mixing are decreased. Two related methods reduce the amplified spontaneous emission power without sacrificing the gain of the optical amplifier. 11 figs.

Single-Mode Near-Infrared Lasing in a GaAsSb-Based Nanowire Superlattice at Room Temperature.

PubMed

Ren, Dingding; Ahtapodov, Lyubomir; Nilsen, Julie S; Yang, Jianfeng; Gustafsson, Anders; Huh, Junghwan; Conibeer, Gavin J; van Helvoort, Antonius T J; Fimland, Bjørn-Ove; Weman, Helge

2018-04-11

Semiconductor nanowire lasers can produce guided coherent light emission with miniaturized geometry, bringing about new possibilities for a variety of applications including nanophotonic circuits, optical sensing, and on-chip and chip-to-chip optical communications. Here, we report on the realization of single-mode and room-temperature lasing from 890 to 990 nm, utilizing a novel design of single nanowires with GaAsSb-based multiple axial superlattices as a gain medium under optical pumping. The control of lasing wavelength via compositional tuning with excellent room-temperature lasing performance is shown to result from the unique nanowire structure with efficient gain material, which delivers a low lasing threshold of ∼6 kW/cm 2 (75 μJ/cm 2 per pulse), a lasing quality factor as high as 1250, and a high characteristic temperature of ∼129 K. These results present a major advancement for the design and synthesis of nanowire laser structures, which can pave the way toward future nanoscale integrated optoelectronic systems with superior performance.

Light scattering and random lasing in aqueous suspensions of hexagonal boron nitride nanoflakes

NASA Astrophysics Data System (ADS)

O'Brien, S. A.; Harvey, A.; Griffin, A.; Donnelly, T.; Mulcahy, D.; Coleman, J. N.; Donegan, J. F.; McCloskey, D.

2017-11-01

Liquid phase exfoliation allows large scale production of 2D materials in solution. The particles are highly anisotropic and strongly scatter light. While spherical particles can be accurately and precisely described by a single parameter—the radius, 2D nanoflakes, however, cannot be so easily described. We investigate light scattering in aqueous solutions of 2D hexagonal boron nitride nanoflakes in the single and multiple scattering regimes. In the single scattering regime, the anisotropic 2D materials show a much stronger depolarization of light when compared to spherical particles of similar size. In the multiple scattering regime, the scattering as a function of optical path for hexagonal boron nitride nanoflakes of a given lateral length was found to be qualitatively equivalent to scattering from spheres with the same diameter. We also report the presence of random lasing in high concentration suspensions of aqueous h-BN mixed with Rhodamine B dye. The h-BN works as a scattering agent and Rhodamine B as a gain medium for the process. We observed random lasing at 587 nm with a threshold energy of 0.8 mJ.

Light scattering and random lasing in aqueous suspensions of hexagonal boron nitride nanoflakes.

PubMed

O'Brien, S A; Harvey, A; Griffin, A; Donnelly, T; Mulcahy, D; Coleman, J N; Donegan, J F; McCloskey, D

2017-11-24

Liquid phase exfoliation allows large scale production of 2D materials in solution. The particles are highly anisotropic and strongly scatter light. While spherical particles can be accurately and precisely described by a single parameter-the radius, 2D nanoflakes, however, cannot be so easily described. We investigate light scattering in aqueous solutions of 2D hexagonal boron nitride nanoflakes in the single and multiple scattering regimes. In the single scattering regime, the anisotropic 2D materials show a much stronger depolarization of light when compared to spherical particles of similar size. In the multiple scattering regime, the scattering as a function of optical path for hexagonal boron nitride nanoflakes of a given lateral length was found to be qualitatively equivalent to scattering from spheres with the same diameter. We also report the presence of random lasing in high concentration suspensions of aqueous h-BN mixed with Rhodamine B dye. The h-BN works as a scattering agent and Rhodamine B as a gain medium for the process. We observed random lasing at 587 nm with a threshold energy of 0.8 mJ.

Continuous-wave lasing in an organic-inorganic lead halide perovskite semiconductor

NASA Astrophysics Data System (ADS)

Jia, Yufei; Kerner, Ross A.; Grede, Alex J.; Rand, Barry P.; Giebink, Noel C.

2017-12-01

Hybrid organic-inorganic perovskites have emerged as promising gain media for tunable, solution-processed semiconductor lasers. However, continuous-wave operation has not been achieved so far1-3. Here, we demonstrate that optically pumped continuous-wave lasing can be sustained above threshold excitation intensities of 17 kW cm-2 for over an hour in methylammonium lead iodide (MAPbI3) distributed feedback lasers that are maintained below the MAPbI3 tetragonal-to-orthorhombic phase transition temperature of T ≈ 160 K. In contrast with the lasing death phenomenon that occurs for pure tetragonal-phase MAPbI3 at T > 160 K (ref. 4), we find that continuous-wave gain becomes possible at T ≈ 100 K from tetragonal-phase inclusions that are photogenerated by the pump within the normally existing, larger-bandgap orthorhombic host matrix. In this mixed-phase system, the tetragonal inclusions function as carrier recombination sinks that reduce the transparency threshold, in loose analogy to inorganic semiconductor quantum wells, and may serve as a model for engineering improved perovskite gain media.

Simultaneous multi-state stimulated emission in quantum dot lasers: experiment and analytical approach

NASA Astrophysics Data System (ADS)

Korenev, V. V.; Savelyev, A. V.; Zhukov, A. E.; Omelchenko, A. V.; Maximov, M. V.; Shernyakov, Yu. M.

2012-06-01

The theoretical investigation of the double-state lasing phenomena in InAs/InGaAs quantum dot lasers has been carried out. The new mechanism of the ground-state lasing quenching, which takes place in quantum dot (QD) laser operating in double-state lasing regime at high pump level, was proposed. The difference between electron and hole capture rates causes the depletion of the hole levels and consequently leads to the decrease of an output lasing power via QD ground state with the growth of injection. Moreover, it was shown that the hole-to-electron capture rates ratio strongly affects both the light-current curve and the key laser parameters. The model of the simultaneous lasing through the ground and excited QD states was developed which allows to describe the observed quenching quantitatively.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, J.; Hao, H.; Li, J. Y.

We report a systematic experimental study of a storage ring two-color free-electron laser (FEL) operating simultaneously in the infrared (IR) and ultraviolet (UV) wavelength regions. The two-color FEL lasing has been realized using a pair of dual-band high-reflectivity FEL mirrors with two different undulator configurations. We have demonstrated independent wavelength tuning in a wide range for each lasing color, as well as harmonically locked wavelength tuning when the UV lasing occurs at the second harmonic of the IR lasing. Precise power control of two-color lasing with good power stability has also been achieved. In addition, the impact of the degradationmore » of FEL mirrors on the two-color FEL operation is reported. Moreover, we have investigated the temporal structures of the two-color FEL beams, showing simultaneous two-color micropulses with their intensity modulations displayed as FEL macropulses.« less

Asymmetric lasing at spectral singularities

NASA Astrophysics Data System (ADS)

Jin, L.

2018-03-01

Scattering coefficients can diverge at spectral singularities. In such situation, the stationary solution becomes a laser solution with outgoing waves only. We explore a parity-time (PT )-symmetric non-Hermitian two-arm Aharonov-Bohm interferometer consisting of three coupled resonators enclosing synthetic magnetic flux. The synthetic magnetic flux does not break the PT symmetry, which protects the symmetric transmission. The features and conditions of symmetric, asymmetric, and unidirectional lasing at spectral singularities are discussed. We elucidate that lasing affected by the interference is asymmetric; asymmetric lasing is induced by the interplay between the synthetic magnetic flux and the system's non-Hermiticity. The product of the left and right transmissions is equal to that of the reflections. Our findings reveal that the synthetic magnetic flux affects light propagation, and the results can be applied in the design of lasing devices.

Theory of lasing action in plasmonic crystals

NASA Astrophysics Data System (ADS)

Cuerda, J.; Rüting, F.; García-Vidal, F. J.; Bravo-Abad, J.

2015-01-01

We theoretically investigate lasing action in plasmonic crystals incorporating optically pumped four-level gain media. By using detailed simulations based on a time-domain generalization of the finite-element method, we show that the excitation of dark plasmonic resonances (via the gain medium) enables accessing the optimal lasing characteristics of the considered class of systems. Moreover, our study reveals that, in general, arrays of nanowires feature lower lasing thresholds and larger slope efficiencies than those corresponding to periodic arrays of subwavelength apertures. These findings are of relevance for further engineering of active devices based on plasmonic crystals.

Lasing of surface-polished polycrystalline Ho: YAG (yttrium aluminum garnet) fiber.

PubMed

Kim, Hyunjun; Hay, Randall S; McDaniel, Sean A; Cook, Gary; Usechak, Nicholas G; Urbas, Augustine M; Shugart, Kathleen N; Lee, HeeDong; Kadhim, Ali H; Brown, Dean P; Griffin, Benjamin; Fair, Geoff E; Corns, Randall G; Potticary, Santeri A; Hopkins, Frank K; Averett, Kent L; Zelmon, David E; Parthasarathy, Triplicane A; Keller, Kristin A

2017-03-20

A polycrystalline 1.5% Ho: YAG fiber with a diameter of 31 µm was prepared. Surface roughness from grain boundary grooving was reduced by polishing, which decreased the fiber scattering coefficient from 76 m^-1 to 35 m^-1. Lasing tests were done on this fiber with a SF57 Schott glass cladding. Lasing was confirmed by spectrum narrowing with threshold pump power lower than 500 mW and a slope efficiency of 7%. To our knowledge, this is the first lasing demonstration from a small diameter polycrystalline ceramic fiber.

HiLASE: development of fully diode pumped disk lasers with high average power

NASA Astrophysics Data System (ADS)

Divoky, M.; Smrz, M.; Chyla, M.; Sikocinski, P.; Severova, P.; Novák, O.; Huynh, J.; Nagisetty, S. S.; Miura, T.; Liberatore, C.; Pilař, J.; Slezak, O.; Sawicka, M.; Jambunathan, V.; Gemini, L.; Vanda, J.; Svabek, R.; Endo, A.; Lucianetti, A.; Rostohar, D.; Mason, P. D.; Phillips, P. J.; Ertel, K.; Banerjee, S.; Hernandez-Gomez, C.; Collier, J. L.; Mocek, T.

2015-02-01

An overview of Czech national R&D project HiLASE (High average power pulsed LASEr) is presented. The HiLASE project aims at development of pulsed DPSSL for hi-tech industrial applications. HiLASE will be a user oriented facility with several laser systems with output parameters ranging from a few picosecond pulses with energy of 5 mJ to 0.5 J and repetition rate of 1-100 kHz (based on thin disk technology) to systems with 100 J output energy in nanosecond pulses with repetition rate of 10 Hz (based on multi-slab technology).

Microring embedded hollow polymer fiber laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Linslal, C. L., E-mail: linslal@gmail.com; Sebastian, S.; Mathew, S.

2015-03-30

Strongly modulated laser emission has been observed from rhodamine B doped microring resonator embedded in a hollow polymer optical fiber by transverse optical pumping. The microring resonator is fabricated on the inner wall of a hollow polymer fiber. Highly sharp lasing lines, strong mode selection, and a collimated laser beam are observed from the fiber. Nearly single mode lasing with a side mode suppression ratio of up to 11.8 dB is obtained from the strongly modulated lasing spectrum. The microring embedded hollow polymer fiber laser has shown efficient lasing characteristics even at a propagation length of 1.5 m.

Single-Mode Near-Infrared Lasing in a GaAsSb-Based Nanowire Superlattice at Room Temperature

NASA Astrophysics Data System (ADS)

Ren, Dingding; Ahtapodov, Lyubomir; Nilsen, Julie S.; Yang, Jianfeng; Gustafsson, Anders; Huh, Junghwan; Conibeer, Gavin J.; van Helvoort, Antonius T. J.; Fimland, Bjørn-Ove; Weman, Helge

2018-04-01

Semiconductor nanowire lasers can produce guided coherent light emission with miniaturized geometry, bringing about new possibility for a variety of applications including nanophotonic circuits, optical sensing, and on-chip and chip-to-chip optical communications. Here, we report on the realization of single-mode room-temperature lasing from 890 nm to 990 nm utilizing a novel design of single nanowires with GaAsSb-based multiple superlattices as gain medium under optical pumping. The wavelength tunability with comprehensively enhanced lasing performance is shown to result from the unique nanowire structure with efficient gain materials, which delivers a lasing quality factor as high as 1250, a reduced lasing threshold ~ 6 kW cm-2 and a high characteristic temperature ~ 129 K. These results present a major advancement for the design and synthesis of nanowire laser structures, which can pave the way towards future nanoscale integrated optoelectronic systems with stunning performance.

Electrically assisted bandedge mode selection of photonic crystal lasing in chiral nematic liquid crystals

NASA Astrophysics Data System (ADS)

Wang, Chun-Ta; Chen, Chun-Wei; Yang, Tzu-Hsuan; Nys, Inge; Li, Cheng-Chang; Lin, Tsung-Hsien; Neyts, Kristiaan; Beeckman, Jeroen

2018-01-01

Selection of the bandedge lasing mode of a photonic crystal laser has been realized in a fluorescent dye doped chiral nematic liquid crystal by exerting electrical control over the mode competition. The bandedge lasing can be reversibly switched from the short-wavelength edge mode to the long-wavelength edge mode by applying a voltage of only 20 V, without tuning the bandgap. The underlying mechanism is the field-induced change in the order parameter of the fluorescent dye in the liquid crystal. The orientation of the transition dipole moment determines the polarization state of the dye emission, thereby promoting lasing in the bandedge mode that favors the emission polarization. Moreover, the dynamic mode-selection capability is retained upon polymer-stabilizing the chiral nematic liquid crystal laser. In the polymer-stabilized system, greatly improved stability and lasing performance are observed.

Storage ring two-color free-electron laser

DOE PAGES

Yan, J.; Hao, H.; Li, J. Y.; ...

2016-07-05

We report a systematic experimental study of a storage ring two-color free-electron laser (FEL) operating simultaneously in the infrared (IR) and ultraviolet (UV) wavelength regions. The two-color FEL lasing has been realized using a pair of dual-band high-reflectivity FEL mirrors with two different undulator configurations. We have demonstrated independent wavelength tuning in a wide range for each lasing color, as well as harmonically locked wavelength tuning when the UV lasing occurs at the second harmonic of the IR lasing. Precise power control of two-color lasing with good power stability has also been achieved. In addition, the impact of the degradationmore » of FEL mirrors on the two-color FEL operation is reported. Moreover, we have investigated the temporal structures of the two-color FEL beams, showing simultaneous two-color micropulses with their intensity modulations displayed as FEL macropulses.« less

Selection of lasing direction in single mode semiconductor square ring cavities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Jin-Woong; Kim, Kyoung-Youm; Moon, Hee-Jong

We propose and demonstrate a selection scheme of lasing direction by imposing a loss imbalance structure into the single mode square ring cavity. The control of the traveling direction is realized by introducing a taper-step section in one of the straight waveguides of the square ring cavity. It was shown by semi-analytic calculation that the taper-step section in the cavity provides effective loss imbalance between two travelling directions as the round trip repeats. Various kinds of square cavities were fabricated using InGaAsP/InGaAs multiple quantum well semiconductor materials in order to test the direction selectivity while maintaining the single mode. Wemore » also measured the pump power dependent lasing spectra to investigate the maintenance property of the lasing direction. The experimental results demonstrated that the proposed scheme is an efficient means for a unidirectional lasing in a single mode laser.« less

Distributed Feedback Laser Based on Single Crystal Perovskite

NASA Astrophysics Data System (ADS)

Sun, Shang; Xiao, Shumin; Song, Qinghai

2017-06-01

We demonstrate a single crystal perovskite based, with grating-structured photoresist on top, highly polarized distributed feedback laser. A lower laser threshold than the Fabry-Perot mode lasers from the same single crystal CH3NH3PbBr3 microplate was obtained. Single crystal CH3NH3PbBr3 microplates was synthesized with one-step solution processed precipitation method. Once the photoresist on top of the microplate was patterned with electron beam, the device was realized. This one-step fabrication process utilized the advantage of single crystal to the greatest extend. The ultra-low defect density in single crystalline microplate offer an opportunity for lower threshold lasing action compare with poly-crystal perovskite films. In the experiment, the lasing action based on the distributed feedback grating design was found with lower threshold and higher intensity than the Fabry-Perot mode lasers supported by the flat facets of the same microplate.

The influence of carrier dynamics on double-state lasing in quantum dot lasers at variable temperature

NASA Astrophysics Data System (ADS)

Korenev, V. V.; Savelyev, A. V.; Zhukov, A. E.; Omelchenko, A. V.; Maximov, M. V.

2014-12-01

It is shown in analytical form that the carrier capture from the matrix as well as carrier dynamics in quantum dots plays an important role in double-state lasing phenomenon. In particular, the de-synchronization of hole and electron captures allows one to describe recently observed quenching of ground-state lasing, which takes place in quantum dot lasers operating in double-state lasing regime at high injection. From the other side, the detailed analysis of charge carrier dynamics in the single quantum dot enables one to describe the observed light-current characteristics and key temperature dependences.

Analytical approach to the multi-state lasing phenomenon in quantum dot lasers

NASA Astrophysics Data System (ADS)

Korenev, V. V.; Savelyev, A. V.; Zhukov, A. E.; Omelchenko, A. V.; Maximov, M. V.

2013-03-01

We introduce an analytical approach to describe the multi-state lasing phenomenon in quantum dot lasers. We show that the key parameter is the hole-to-electron capture rate ratio. If it is lower than a certain critical value, the complete quenching of ground-state lasing takes place at high injection levels. At higher values of the ratio, the model predicts saturation of the ground-state power. This explains the diversity of experimental results and their contradiction to the conventional rate equation model. Recently found enhancement of ground-state lasing in p-doped samples and temperature dependence of the ground-state power are also discussed.

Multi-state lasing in self-assembled ring-shaped green fluorescent protein microcavities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dietrich, Christof P., E-mail: cpd3@st-andrews.ac.uk; Höfling, Sven; Gather, Malte C., E-mail: mcg6@st-andrews.ac.uk

2014-12-08

We demonstrate highly efficient lasing from multiple photonic states in microcavities filled with self-assembled rings of recombinant enhanced green fluorescent protein (eGFP) in its solid state form. The lasing regime is achieved at very low excitation energies of 13 nJ and occurs from cavity modes dispersed in both energy and momentum. We attribute the momentum distribution to very efficient scattering of incident light at the surface of the eGFP rings. The distribution of lasing states in energy is induced by the large spectral width of the gain spectrum of recombinant eGFP (FWHM ≅ 25 nm)

Lasing by driven atoms-cavity system in collective strong coupling regime.

PubMed

Sawant, Rahul; Rangwala, S A

2017-09-12

The interaction of laser cooled atoms with resonant light is determined by the natural linewidth of the excited state. An optical cavity is another optically resonant system where the loss from the cavity determines the resonant optical response of the system. The near resonant combination of an optical Fabry-Pérot cavity with laser cooled and trapped atoms couples two distinct optical resonators via light and has great potential for precision measurements and the creation of versatile quantum optics systems. Here we show how driven magneto-optically trapped atoms in collective strong coupling regime with the cavity leads to lasing at a frequency red detuned from the atomic transition. Lasing is demonstrated experimentally by the observation of a lasing threshold accompanied by polarization and spatial mode purity, and line-narrowing in the outcoupled light. Spontaneous emission into the cavity mode by the driven atoms stimulates lasing action, which is capable of operating as a continuous wave laser in steady state, without a seed laser. The system is modeled theoretically, and qualitative agreement with experimentally observed lasing is seen. Our result opens up a range of new measurement possibilities with this system.

Symmetry, stability, and computation of degenerate lasing modes

NASA Astrophysics Data System (ADS)

Liu, David; Zhen, Bo; Ge, Li; Hernandez, Felipe; Pick, Adi; Burkhardt, Stephan; Liertzer, Matthias; Rotter, Stefan; Johnson, Steven G.

2017-02-01

We present a general method to obtain the stable lasing solutions for the steady-state ab initio lasing theory (SALT) for the case of a degenerate symmetric laser in two dimensions (2D). We find that under most regimes (with one pathological exception), the stable solutions are clockwise and counterclockwise circulating modes, generalizing previously known results of ring lasers to all 2D rotational symmetry groups. Our method uses a combination of semianalytical solutions close to lasing threshold and numerical solvers to track the lasing modes far above threshold. Near threshold, we find closed-form expressions for both circulating modes and other types of lasing solutions as well as for their linearized Maxwell-Bloch eigenvalues, providing a simple way to determine their stability without having to do a full nonlinear numerical calculation. Above threshold, we show that a key feature of the circulating mode is its "chiral" intensity pattern, which arises from spontaneous symmetry breaking of mirror symmetry, and whose symmetry group requires that the degeneracy persists even when nonlinear effects become important. Finally, we introduce a numerical technique to solve the degenerate SALT equations far above threshold even when spatial discretization artificially breaks the degeneracy.

Harmonic lasing in x-ray free electron lasers

NASA Astrophysics Data System (ADS)

Schneidmiller, E. A.; Yurkov, M. V.

2012-08-01

Harmonic lasing in a free electron laser with a planar undulator (under the condition that the fundamental frequency is suppressed) might be a cheap and efficient way of extension of wavelength ranges of existing and planned x-ray free electron laser (FEL) facilities. Contrary to nonlinear harmonic generation, harmonic lasing can provide much more intense, stable, and narrow-band FEL beam which is easier to handle due to the suppressed fundamental frequency. In this paper we perform a parametrization of the solution of the eigenvalue equation for lasing at odd harmonics, and present an explicit expression for FEL gain length, taking into account all essential effects. We propose and discuss methods for suppression of the fundamental harmonic. We also suggest a combined use of harmonic lasing and lasing at the retuned fundamental wavelength in order to reduce bandwidth and to increase brilliance of x-ray beam at saturation. Considering 3rd harmonic lasing as a practical example, we come to the conclusion that it is much more robust than usually thought, and can be widely used in the existing or planned x-ray FEL (XFEL) facilities. In particular, Linac Coherent Light Source (LCLS) after a minor modification can lase to saturation at the 3rd harmonic up to the photon energy of 25-30 keV providing multigigawatt power level and narrow bandwidth. As for the European XFEL, harmonic lasing would allow one to extend operating range (ultimately up to 100 keV), to reduce FEL bandwidth and to increase brilliance, to enable two-color operation for pump-probe experiments, and to provide more flexible operation at different electron energies. Similar improvements can be realized in other x-ray FEL facilities with gap-tunable undulators like FLASH II, SACLA, LCLS II, etc. Harmonic lasing can be an attractive option for compact x-ray FELs (driven by electron beams with a relatively low energy), allowing the use of the standard undulator technology instead of small-gap in-vacuum devices. Finally, in this paper we discover that in a part of the parameter space, corresponding to the operating range of soft x-ray beam lines of x-ray FEL facilities (like SASE3 beam line of the European XFEL), harmonics can grow faster than the fundamental wavelength. This feature can be used in some experiments, but might also be an unwanted phenomenon, and we discuss possible measures to diminish it.

Multiwavelength fiber laser

NASA Astrophysics Data System (ADS)

Das, Goutam

This thesis studies experimentally and theoretically a few designs of multiwavelength fiber lasers. Four different configurations are proposed and demonstrated; all of which can operate at room temperatures. An elliptical core erbium-doped fiber is used as the gain medium, which is single mode along the minor axis and multimode along the major axis. The principle of operation is based on the anisotropic gain effect of an elliptical core erbium-doped fiber. Stable multiwavelength operation is achieved at room temperatures. A polarization controller is used to control and select the lasing wavelengths. The stability of the lasing lines, in the presence of anisotropic gain effects, has been examined. The maximum number of stable lasing lines that may be obtained depends on the number of modes supported by the erbium-doped fiber. The effects of the dimensions of the fiber are also studied. A ring resonator is formed using an elliptical core erbium-doped fiber. The basic theoretical expression for the threshold pump power for each lasing line is developed. The theoretical results are in excellent agreement with the values obtained experimentally. The dependence of the separations between the lasing wavelengths on the dimensions of the erbium-doped fiber is examined. A theoretical study of a Sagnac loop interferometer and its applications in a passive ring resonator is reported. A ring resonator is formed by using the Sagnac loop filter in the cavity. The experimental results show that the separations between the lasing wavelengths may be controlled by adjusting the birefringence of the Sagnac loop interferometer. These experimental results agree with the theoretical findings. Similarly, another resonator is formed using a Sagnac loop reflector and a broadband reflector in a Fabry-Perot configuration. An optical switch is made, where two wavelengths may be switched by using a polarization controller in the cavity. To study the stability of the lasing wavelengths, the outputs of the lasers are monitored for a few hours using an optical spectrum analyzer with a resolution bandwidth of 0.06 nm. The experimental results show that intensity fluctuations of the lasing lines of less than 0.2 dB are possible with no changes in wavelength. High concentrations of erbium in the fiber degrade the stability of the lasing wavelengths resulting in greater intensity fluctuations. The lasers may be made to lase in the C band or L band by adjusting the length of the erbium-doped fiber in the cavity.

Characterization of Upper-Troposphere Water Vapor Measurements during AFWEX Using LASE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferrare, Richard; Browell, E. V.; Ismail, S.

Water vapor profiles from NASA's Lidar Atmospheric Sensing Experiment (LASE) system acquired during the ARM/FIRE Water Vapor Experiment (AFWEX) are used to characterize upper troposphere water vapor (UTWV) measured by ground-based Raman lidars, radiosondes, and in situ aircraft sensors over the Department of Energy Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site in northern Oklahoma. LASE was deployed from the NASA DC-8 aircraft and measured water vapor over the ARM SGP Central Facility (CF) site during seven flights between November 27 and December 10, 2000. Initially, the DOE ARM SGP Cloud and Radiation Testbed (CART) Raman lidar (CARL) UTWVmore » profiles were about 5-7% wetter than LASE in the upper troposphere, and the Vaisala RS80-H radiosonde profiles were about 10% drier than LASE between 8-12 km. Scaling the Vaisala water vapor profiles to match the precipitable water vapor (PWV) measured by the ARM SGP microwave radiometer (MWR) did not change these results significantly. By accounting for an overlap correction of the CARL water vapor profiles and by employing schemes designed to correct the Vaisala RS80-H calibration method and account for the time response of the Vaisala RS80H water vapor sensor, the average differences between the CARL and Vaisala radiosonde upper troposphere water vapor profiles are reduced to about 5%, which is within the ARM goal of mean differences of less than 10%. The LASE and DC-8 in situ Diode Laser Hygrometer (DLH) UTWV measurements generally agreed to within about 3 to 4%. The DC-8 in situ frost point cryogenic hygrometer and Snow White chilled mirror measurements were drier than the LASE, Raman lidars, and corrected Vaisala RS80H measurements by about 10-25% and 10-15%, respectively. Sippican (formerly VIZ manufacturing) carbon hygristor radiosondes exhibited large variabilities and poor agreement with the other measurements. PWV derived from the LASE profiles agreed to within about 3% on average with PWV derived from the ARM SGP microwave radiometer. The agreement between the LASE and MWR PWV and the LASE and CARL UTWV measurements supports the hypotheses that MWR measurements of the 22 GHz water vapor line can accurately constrain the total water vapor amount and that the CART Raman lidar, when calibrated using the MWR PWV, can provide an accurate, stable reference for characterizing upper troposphere water vapor.« less

LASE measurements of water vapor and aerosol profiles during the Plains Elevated Convection at Night (PECAN) field experiment

NASA Astrophysics Data System (ADS)

Nehrir, A. R.; Ferrare, R. A.; Kooi, S. A.; Butler, C. F.; Notari, A.; Hair, J. W.; Collins, J. E., Jr.; Ismail, S.

2015-12-01

The Lidar Atmospheric Sensing Experiment (LASE) system was deployed on the NASA DC-8 aircraft during the Plains Elevated Convection At Night (PECAN) field experiment, which was conducted during June-July 2015 over the central and southern plains. LASE is an active remote sensor that employs the differential absorption lidar (DIAL) technique to measure range resolved profiles of water vapor and aerosols above and below the aircraft. The DC-8 conducted nine local science flights from June 30- July 14 where LASE sampled water vapor and aerosol fields in support of the PECAN primary science objectives relating to better understanding nocturnal Mesoscale Convective Systems (MCSs), Convective Initiation (CI), the Low Level Jet (LLJ), bores, and to compare different airborne and ground based measurements. LASE observed large spatial and temporal variability in water vapor and aerosol distributions in advance of nocturnal MCSs, across bores resulting from MCS outflow boundaries, and across the LLJ associated with the development of MCSs and CI. An overview of the LASE data collected during the PECAN field experiment will be presented where emphasis will be placed on variability of water vapor profiles in the vicinity of severe storms and intense convection in the central and southern plains. Preliminary comparisons show good agreement between coincident LASE and radiosonde water vapor profiles. In addition, an advanced water vapor DIAL system being developed at NASA Langley will be discussed.

Temperature and current coefficients of lasing wavelength in tunable diode laser spectroscopy.

PubMed

Fukuda, M; Mishima, T; Nakayama, N; Masuda, T

2010-08-01

The factors determining temperature and current coefficients of lasing wavelength are investigated and discussed under monitoring CO(2)-gas absorption spectra. The diffusion rate of Joule heating at the active layer to the surrounding region is observed by monitoring the change in the junction voltage, which is a function of temperature and the wavelength (frequency) deviation under sinusoidal current modulation. Based on the experimental results, the time interval of monitoring the wavelength after changing the ambient temperature or injected current (scanning rate) has to be constant at least to eliminate the monitoring error induced by the deviation of lasing wavelength, though the temperature and current coefficients of lasing wavelength differ with the rate.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Podoskin, A. A., E-mail: podoskin@mail.ioffe.ru; Shashkin, I. S.; Slipchenko, S. O.

A model describing the operation of a completely optical cell, based on the competition of lasing of Fabry-Perot cavity modes and the high-Q closed mode in high-power semiconductor lasers is proposed. Based on rate equations, the conditions of lasing switching between Fabry-Perot modes for ground and excited lasing levels and the closed mode are considered in the case of increasing internal optical loss under conditions of high current pump levels. The optical-cell operation conditions in the mode of a high-power laser radiation switch (reversible mode-structure switching) and in the mode of a memory cell with bistable irreversible lasing switching betweenmore » mode structures with various Q-factors are considered.« less

LASERS, ACTIVE MEDIA: The aqueous-polyelectrolyte dye solution as an active laser medium

NASA Astrophysics Data System (ADS)

Akimov, A. I.; Saletskii, A. M.

2000-11-01

The spectral, luminescent, and lasing properties of aqueous solutions of a cationic dye rhodamine 6G with additions of anion polyelectrolytes — polyacrylic and polymethacrylic acids — are studied. It is found that the energy and spectral properties of lasing of these solutions depend on the ratio of concentrations of polyelectrolyte and molecules. It is also found that the lasing parameters of aqueous-polyelectrolyte dye solutions can be controlled by changing the structure of the molecular system. The variation in the structure of aqueous-polyelectrolyte dye solutions of rhodamine 6G resulted in an almost five-fold increase in the lasing efficiency compared to that in aqueous dye solutions.

Ultraviolet random lasing action from highly disordered n-AlN/p-GaN heterojunction.

PubMed

Yang, H Y; Yu, S F; Wong, J I; Cen, Z H; Liang, H K; Chen, T P

2011-05-01

Room-temperature random lasing is achieved from an n-AlN/p-GaN heterojunction. The highly disordered n-AlN layer, which was deposited on p-GaN:Mg layer via radio frequency magnetron sputtering, acts as a scattering medium to sustain coherent optical feedback. The p-GaN:Mg layer grown on sapphire provides optical amplification to the scattered light propagating along the heterojunction. Hence, lasing peaks of line width less than 0.4 nm are emerged from the emission spectra at round 370 nm for the heterojunction under forward bias larger than 5.1 V. Lasing characteristics of the heterojunction are in agreement with the behavior of random lasers.

Frequency-doubled vertical-external-cavity surface-emitting laser

DOEpatents

Raymond, Thomas D.; Alford, William J.; Crawford, Mary H.; Allerman, Andrew A.

2002-01-01

A frequency-doubled semiconductor vertical-external-cavity surface-emitting laser (VECSEL) is disclosed for generating light at a wavelength in the range of 300-550 nanometers. The VECSEL includes a semiconductor multi-quantum-well active region that is electrically or optically pumped to generate lasing at a fundamental wavelength in the range of 600-1100 nanometers. An intracavity nonlinear frequency-doubling crystal then converts the fundamental lasing into a second-harmonic output beam. With optical pumping with 330 milliWatts from a semiconductor diode pump laser, about 5 milliWatts or more of blue light can be generated at 490 nm. The device has applications for high-density optical data storage and retrieval, laser printing, optical image projection, chemical-sensing, materials processing and optical metrology.

Statistical parity-time-symmetric lasing in an optical fibre network.

PubMed

Jahromi, Ali K; Hassan, Absar U; Christodoulides, Demetrios N; Abouraddy, Ayman F

2017-11-07

Parity-time (PT)-symmetry in optics is a condition whereby the real and imaginary parts of the refractive index across a photonic structure are deliberately balanced. This balance can lead to interesting optical phenomena, such as unidirectional invisibility, loss-induced lasing, single-mode lasing from multimode resonators, and non-reciprocal effects in conjunction with nonlinearities. Because PT-symmetry has been thought of as fragile, experimental realisations to date have been usually restricted to on-chip micro-devices. Here, we demonstrate that certain features of PT-symmetry are sufficiently robust to survive the statistical fluctuations associated with a macroscopic optical cavity. We examine the lasing dynamics in optical fibre-based coupled cavities more than a kilometre in length with balanced gain and loss. Although fluctuations can detune the cavity by more than the free spectral range, the behaviour of the lasing threshold and the laser power is that expected from a PT-stable system. Furthermore, we observe a statistical symmetry breaking upon varying the cavity loss.

Effects of XeCl excimer lasers and fluoride application on artificial caries-like lesions

NASA Astrophysics Data System (ADS)

Wilder-Smith, Petra B. B.; Phan, T.; Liaw, Lih-Huei L.; Berns, Michael W.

1994-09-01

In this study the affects of a pulsed excimer laser emitting at 308 nm (XeCl) on enamel susceptibility to artificial caries-like lesions were investigated. Additional effects of fluoride (F) application were also studied and SEC examinations performed. Sixty-four extracted human molar teeth were coated with acid resistant varnish leaving four windows, then sectioned, leaving one window on each tooth quarter. The windows were treated in one of the following ways: untreated (control), or lased, or exposed to 4 min. APF (1.23% F) before lasing, or exposed to 4 min. APF (1.23% F) after lasing. After lasing, microhardness profiles were obtained and SEM was performed. Caries resistance was generally increased at moderate fluences. F application combined with lasing enhanced caries resistance at some parameters. SEM showed effects ranging from minimal to localized effects to extended glazing. Pulsed excimer laser irradiation, especially combined with topical F application can inhibit development of artificial caries-like lesions.

Lasing in optimized two-dimensional iron-nail-shaped rod photonic crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwon, Soon-Yong; Moon, Seul-Ki; Yang, Jin-Kyu, E-mail: jinkyuyang@kongju.ac.kr

2016-03-15

We demonstrated lasing at the Γ-point band-edge (BE) modes in optimized two-dimensional iron-nail-shaped rod photonic crystals by optical pulse pumping at room temperature. As the radius of the rod increased quadratically toward the edge of the pattern, the quality factor of the Γ-point BE mode increased up to three times, and the modal volume decreased to 56% compared with the values of the original Γ-point BE mode because of the reduction of the optical loss in the horizontal direction. Single-mode lasing from an optimized iron-nail-shaped rod array with an InGaAsP multiple quantum well embedded in the nail heads was observedmore » at a low threshold pump power of 160 μW. Real-image-based numerical simulations showed that the lasing actions originated from the optimized Γ-point BE mode and agreed well with the measurement results, including the lasing polarization, wavelength, and near-field image.« less

Proposal for ultrasmall deep ultraviolet diamond Raman nanolaser

NASA Astrophysics Data System (ADS)

Kim, Kwang-Hyon; Choe, Song-Hyok

2016-10-01

We propose diamond nanoparticle Raman laser operating in the spectral range of deep ultraviolet. High Raman gain and low cavity loss of diamond nanoparticles enable low-threshold Raman lasing. Based on the coupled-mode theory, we numerically study its lasing dynamics. For the diamond nanoparticle with a radius of about 130 nm, the lasing threshold energy is below 10 pJ for a pump spot size of 1 μm.

Degenerate band edge laser

NASA Astrophysics Data System (ADS)

Veysi, Mehdi; Othman, Mohamed A. K.; Figotin, Alexander; Capolino, Filippo

2018-05-01

We propose a class of lasers based on a fourth-order exceptional point of degeneracy (EPD) referred to as the degenerate band edge (DBE). EPDs have been found in parity-time-symmetric photonic structures that require loss and/or gain; here we show that the DBE is a different kind of EPD since it occurs in periodic structures that are lossless and gainless. Because of this property, a small level of gain is sufficient to induce single-frequency lasing based on a synchronous operation of four degenerate Floquet-Bloch eigenwaves. This lasing scheme constitutes a light-matter interaction mechanism that leads also to a unique scaling law of the laser threshold with the inverse of the fifth power of the laser-cavity length. The DBE laser has the lowest lasing threshold in comparison to a regular band edge laser and to a conventional laser in cavities with the same loaded quality (Q ) factor and length. In particular, even without mirror reflectors the DBE laser exhibits a lasing threshold which is an order of magnitude lower than that of a uniform cavity laser of the same length and with very high mirror reflectivity. Importantly, this novel DBE lasing regime enforces mode selectivity and coherent single-frequency operation even for pumping rates well beyond the lasing threshold, in contrast to the multifrequency nature of conventional uniform cavity lasers.

Multiplexed lasing in tissues

NASA Astrophysics Data System (ADS)

Chen, Yu-Cheng; Chen, Qiushu; Fan, Xudong

2017-02-01

Biolasers are an emerging technology for next generation biochemical detection and clinical applications. Progress has recently been made to achieve lasing from biomolecules and single living cells. Tissues, which consist of cells embedded in extracellular matrix, mimic more closely the actual complex biological environment in a living body and therefore are of more practical significance. Here, we developed a highly versatile tissue laser platform, in which tissues stained with fluorophores are sandwiched in a high-Q Fabry-Pérot microcavity. Distinct lasing emissions from muscle and adipose tissues stained respectively with fluorescein isothiocyanate (FITC) and boron-dipyrromethene (BODIPY), and hybrid muscle/adipose tissue with dual-staining were achieved with a threshold of only 10 μJ/mm2. Additionally, we investigated how tissue structure/geometry, tissue thickness, and staining dye concentration affect the tissue laser. It is further found that, despite large fluorescence spectral overlap between FITC and BODIPY in tissues, their lasing emissions could be clearly distinguished and controlled due to their narrow lasing bands and different lasing thresholds, thus enabling highly multiplexed detection. Our tissue laser platform can be broadly applicable to various types of tissues/diseases. It provides a new tool for a wide range of biological and biomedical applications, such as diagnostics/screening of tissues and identification/monitoring of biological transformations in tissue engineering.

Very Low Threshold ASE and Lasing Using Auger-Suppressed Nanocrystal Quantum Dots

NASA Astrophysics Data System (ADS)

Park, Young-Shin; Bae, Wan Ki; Fidler, Andrew; Baker, Tomas; Lim, Jaehoon; Pietryga, Jeffrey; Klimov, Victor

2015-03-01

We report amplified spontaneous emission (ASE) and lasing with very low thresholds obtained using thin films made of engineered thick-shell CdSe/CdS QDs that have a CdSeS alloyed layer between the CdSe core and the CdS shell. These ``alloyed'' QDs exhibit considerable reduction of Auger decay rates, which results in high biexciton emission quantum yields (QBX of ~ 12%) and extended biexciton lifetimes (τBX of ~ 4ns). By using a fs laser (400 nm at 1 kHz repetition rate) as a pump source, we measured the threshold intensity of biexciton ASE as low as 5 μJ/cm2, which is about 5 times lower than the lowest ASE thresholds reported for thick-shell QDs without interfacial alloying. Interestingly, we also observed biexciton random lasing from the same QD film. Lasing spectrum comprises several sharp peaks (linewidth ~0.2 nm), and the heights and the spectral positions of these peaks show strong dependence on the exact position of the excitation spot on the QD film. Our study suggests that further suppression of nonradiative Auger decay rates via even finer grading of the core/shell interface could lead to a further reduction in the lasing threshold and potentially realization of lasing under continuous-wave excitation.

First pulse effect self-suppression picosecond regenerative amplifier (Conference Presentation)

NASA Astrophysics Data System (ADS)

Fan, Haitao; Chang, Liang; Zhang, Yi; Yao, Siyi; Lu, Wei; Yang, Xiaohong

2017-03-01

First pulse effect, commonly seen in nanosecond cavity-dumped lasers and picosecond regenerative amplifiers, not only leads to degradation of processing quality, but also acts as potential threat to optical switching elements. Several methods have been developed to suppress that effect, including electronic controls, polarization controls, and diffraction controls. We present a new way for first pulse self-suppression without any additional components. By carefully arranging the cavity mirror of a regenerative amplifier, we realized `parasitic lasing like' radiation. When the regenerative amplifier works in `operation ready' status, the parasitic lasing occurs and prevents the gain crystal from saturation. When the regenerative amplifier starts working and amplifying pulses, the first pulse in a pulse train will not get much more gain and energy than pulses following it. As parasitic lasing disappears at the same time, the average output power of the amplifier does not significantly reduce. This cost effective method does not require any additional component. In addition, as it is not polarization dependent, this method is widely suitable for different kinds of regenerative amplifiers. It's the easiest and cheapest way to suppress first pulse effect, to the best of our knowledge.

Violet-to-Blue Gain and Lasing from Colloidal CdS Nanoplatelets: Low-Threshold Stimulated Emission Despite Low Photoluminescence Quantum Yield

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diroll, Benjamin T.; Talapin, Dmitri V.; Schaller, Richard D.

Amplified spontaneous emission (ASE) and lasing from solution-processed materials are demonstrated in the challenging violet-to-blue (430–490 nm) spectral region for colloidal nanoplatelets of CdS and newly synthesized core/shell CdS/ZnS nanoplatelets. Despite modest band-edge photoluminescence quantum yields of 2% or less for single excitons, which we show results from hole trapping, the samples exhibit low ASE thresholds. Furthermore, four-monolayer CdS samples show ASE at shorter wavelengths than any reported film of colloidal quantum-confined material. This work underlines that low quantum yields for single excitons do not necessarily lead to a poor gain medium. The low ASE thresholds originate from negligible dispersionmore » in thickness, large absorption cross sections of 2.8 × 10–14 cm–2, and rather slow (150 to 300 ps) biexciton recombination. We show that under higher-fluence excitation, ASE can kinetically outcompete hole trapping. Using nanoplatelets as the gain medium, lasing is observed in a linear optical cavity. This work confirms the fundamental advantages of colloidal quantum well structures as gain media, even in the absence of high photoluminescence efficiency.« less

Individualized FAC on bottom tab subassemblies to minimize adhesive gap between emitter and optics

NASA Astrophysics Data System (ADS)

Sauer, Sebastian; Müller, Tobias; Haag, Sebastian; Beleke, Andreas; Zontar, Daniel; Baum, Christoph; Brecher, Christian

2017-02-01

High Power Diode Laser (HPDL) systems with short focal length fast-axis collimators (FAC) require submicron assembly precision. Conventional FAC-Lens assembly processes require adhesive gaps of 50 microns or more in order to compensate for component tolerances (e.g. deviation of back focal length) and previous assembly steps. In order to control volumetric shrinkage of fast-curing UV-adhesives shrinkage compensation is mandatory. The novel approach described in this paper aims to minimize the impact of volumetric shrinkage due to the adhesive gap between HPDL edge emitters and FAC-Lens. Firstly, the FAC is actively aligned to the edge emitter without adhesives or bottom tab. The relative position and orientation of FAC to emitter are measured and stored. Consecutively, an individual subassembly of FAC and bottom tab is assembled on Fraunhofer IPT's mounting station with a precision of +/-1 micron. Translational and lateral offsets can be compensated, so that a narrow and uniform glue gap for the consecutive bonding process of bottom tab to heatsink applies (Figure 4). Accordingly, FAC and bottom tab are mounted to the heatsink without major shrinkage compensation. Fraunhofer IPT's department assembly of optical systems and automation has made several publications regarding active alignment of FAC lenses [SPIE LASE 8241-12], volumetric shrinkage compensation [SPIE LASE 9730-28] and FAC on bottom tab assembly [SPIE LASE 9727-31] in automated production environments. The approach described in this paper combines these and is the logical continuation of that work towards higher quality of HPDLs.

Ultralow-threshold Raman lasing with CaF2 resonators.

PubMed

Grudinin, Ivan S; Maleki, Lute

2007-01-15

We demonstrate efficient Raman lasing with CaF2 whispering-gallery-mode resonators. Continuous-wave emission threshold is shown to be possible below 1 microW with a 5mm cavity, which is to our knowledge orders of magnitude lower than in any other Raman source. Low-threshold lasing is made possible by the ultrahigh optical quality factor of the cavity, of the order of Q=5x10(10). Stokes components of up to the fifth order were observed at a pump power of 160 microW, and up to the eighth order at 1 mW. A lasing threshold of 15 microW was also observed in a 100 microm CaF2 microcavity. Potential applications are discussed.

Influence of reabsorption and reemission on stimulated Raman scattering of polymethine dyes in multiple scattering media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yashchuk, V P; Komyshan, A O; Smaliuk, A P

2013-12-31

It is shown that reabsorption of the luminescence radiation in the range of its overlapping with the absorption spectrum and the following reemission to a long-wavelength range may noticeably affect the process of stimulated Raman scattering (SRS) in polymethine dyes in multiple scattering media (MSM). This is related to the fact that SRS in such media occurs jointly with the random lasing (RL), which favors SRS and makes up with it a united nonlinear process. Reemission into the long-wavelength spectrum range amplified in MSM causes the RL spectrum to shift to longer wavelengths and initiates the long-wavelength band of RL,more » in which a main part of the lasing energy is concentrated. This weakens or completely stops the SRS if the band is beyond the range of possible spectral localisation of Stokes lines. This process depends on the efficiency of light scattering, dye concentration, temperature and pump intensity; hence, there exist optimal values of these parameters for obtaining SRS in MSM. (nonlinear optical phenomena)« less

Optically pumped isotopic ammonia laser system

DOEpatents

Buchwald, Melvin I.; Jones, Claude R.; Nelson, Leonard Y.

1982-01-01

An optically pumped isotopic ammonia laser system which is capable of producing a plurality of frequencies in the middle infrared spectral region. Two optical pumping mechanisms are disclosed, i.e., pumping on R(J) and lasing on P(J) in response to enhancement of rotational cascade lasing including stimulated Raman effects, and, pumping on R(J) and lasing on P(J+2). The disclosed apparatus for optical pumping include a hole coupled cavity and a grating coupled cavity.

Laser beam distribution system for the HiLASE Center

NASA Astrophysics Data System (ADS)

Macúchová, Karolina; Heřmánek, Jan; Kaufman, Jan; Muresan, Mihai-George; Růžička, Jan; Řeháková, Martina; Divoký, Martin; Švandrlík, Luděk.; Mocek, Tomáś

2017-12-01

We report recent progress in design and testing of a distribution system for high-power laser beam delivery developed within the HiLASE project of the IOP in the Czech Republic. Laser beam distribution system is a technical system allowing safe and precise distribution of different laser beams from laboratories to several experimental stations. The unique nature of HiLASE lasers requires new approach, which makes design of the distribution system a state-of-the-art challenge.

Gallium nitride nanotube lasers

DOE PAGES

Li, Changyi; Liu, Sheng; Hurtado, Antonio; ...

2015-01-01

Lasing is demonstrated from gallium nitride nanotubes fabricated using a two-step top-down technique. By optically pumping, we observed characteristics of lasing: a clear threshold, a narrow spectral, and guided emission from the nanotubes. In addition, annular lasing emission from the GaN nanotube is also observed, indicating that cross-sectional shape control can be employed to manipulate the properties of nanolasers. The nanotube lasers could be of interest for optical nanofluidic applications or application benefitting from a hollow beam shape.

Innovative FEL schemes using variable-gap undulators

NASA Astrophysics Data System (ADS)

Schneidmiller, E. A.; Yurkov, M. V.

2017-06-01

We discuss theoretical background and experimental verification of advanced schemes for X-ray FELs using variable gap undulators (harmonic lasing self-seeded FEL, reverse taper etc.) Harmonic lasing in XFELs is an opportunity to extend operating range of existing and planned X-ray FEL user facilities. Contrary to nonlinear harmonic generation, harmonic lasing can provide much more intense, stable, and narrow-band FEL beam which is easier to handle due to the suppressed fundamental. Another interesting application of harmonic lasing is Harmonic Lasing Self-Seeded (HLSS) FEL that allows to improve longitudinal coherence and spectral power of a SASE FEL. Recently this concept was successfully tested at the soft X-ray FEL user facility FLASH in the wavelength range between 4.5 nm and 15 nm. That was also the first experimental demonstration of harmonic lasing in a high-gain FEL and at a short wavelength (before it worked only in infrared FEL oscillators). Another innovative scheme that was tested at FLASH2 is the reverse tapering that can be used to produce circularly polarized radiation from a dedicated afterburner with strongly suppressed linearly polarized radiation from the main undulator. This scheme can also be used for an efficient background-free production of harmonics in an afterburner. Experiments on the frequency doubling that allowed to reach the shortest wavelength at FLASH as well as on post-saturation tapering to produce a record intencity in XUV regime are also discussed.

Improving the efficiency of x-ray lasers

NASA Astrophysics Data System (ADS)

Tallents, Gregory J.; Zeitoun, Philippe; Behjat, A.; Demir, A.; Holden, M.; Krishnan, J.; Lewis, Ciaran L. S.; MacPhee, Andrew G.; Warwick, P. J.; Nantel, Marc; Jamelot, Gerard; Rus, Bedrich; Jaegle, Pierre; Klisnick, Annie; Goedtkindt, P.; Carillon, Antoine; Fill, Ernst E.; Li, Yuelin; Pretzler, Georg; Schloegl, Dieter; Steingruber, Juergen; Neely, David; Norreys, Peter A.; Key, Michael H.; Zhang, Jie; Pert, Geoffrey J.; Healy, S. B.; Plowes, J. A.

1995-09-01

Current successful approaches for achieving soft x-ray lasing typically require pumping laser pulses of duration approximately ns and energy approximately kJ (collisionally pumped schemes) or approximately ps pulses and powers of approximately several TW (recombination-pumped schemes). For applications, it is important to improve the efficiency of soft x-ray lasers and so reduce the required power of pumping lasers. The effect of pre- pulse on neon-like collisionally pumped lasers has been investigated using the LULI laser (Ecole Polytechnique, France). A small pre-pulse level approximately 10-3 of the main pulse energy was found to increase the J equals 0 minus 1 neon-like zinc laser output at 21 nm by an order-of-magnitude with a comparable increase in efficiency. A double pumping laser pulse on neon-like yttrium lasing output at 15 nm obtained with the VULCAN laser (Rutherford Appleton Laboratory, England) was also found to increase the x-ray lasing efficiency. With adiabatically cooled recombination lasing, it is shown that approximately 2 ps pulses are optimum for achieving the desired ionization balance for lasing output. The possibility of achieving recombination lasing at short wavelengths on lithium-like ions with longer pulse lasers has been investigated using the ASTERIX laser (Max-Planck Quantenoptik, Germany). These results are presented and interpreted to provide possible directions for improving the efficiency of x-ray lasers.

Ultralow-threshold multiphoton-pumped lasing from colloidal nanoplatelets in solution

PubMed Central

Li, Mingjie; Zhi, Min; Zhu, Hai; Wu, Wen-Ya; Xu, Qing-Hua; Jhon, Mark Hyunpong; Chan, Yinthai

2015-01-01

Although multiphoton-pumped lasing from a solution of chromophores is important in the emerging fields of nonlinear optofluidics and bio-photonics, conventionally used organic dyes are often rendered unsuitable because of relatively small multiphoton absorption cross-sections and low photostability. Here, we demonstrate highly photostable, ultralow-threshold multiphoton-pumped biexcitonic lasing from a solution of colloidal CdSe/CdS nanoplatelets within a cuvette-based Fabry–Pérot optical resonator. We find that colloidal nanoplatelets surprisingly exhibit an optimal lateral size that minimizes lasing threshold. These nanoplatelets possess very large gain cross-sections of 7.3 × 10−14 cm2 and ultralow lasing thresholds of 1.2 and 4.3 mJ cm−2 under two-photon (λexc=800 nm) and three-photon (λexc=1.3 μm) excitation, respectively. The highly polarized emission from the nanoplatelet laser shows no significant photodegradation over 107 laser shots. These findings constitute a more comprehensive understanding of the utility of colloidal semiconductor nanoparticles as the gain medium in high-performance frequency-upconversion liquid lasers. PMID:26419950

Miscellaneous Lasing Actions in Organo-Lead Halide Perovskite Films.

PubMed

Duan, Zonghui; Wang, Shuai; Yi, Ningbo; Gu, Zhiyuan; Gao, Yisheng; Song, Qinghai; Xiao, Shumin

2017-06-21

Lasing actions in organo-lead halide perovskite films have been heavily studied in the past few years. However, due to the disordered nature of synthesized perovskite films, the lasing actions are usually understood as random lasers that are formed by multiple scattering. Herein, we demonstrate the miscellaneous lasing actions in organo-lead halide perovskite films. In addition to the random lasers, we show that a single or a few perovskite microparticles can generate laser emissions with their internal resonances instead of multiple scattering among them. We experimentally observed and numerically confirmed whispering gallery (WG)-like microlasers in polygon shaped and other deformed microparticles. Meanwhile, owing to the nature of total internal reflection and the novel shape of the nanoparticle, the size of the perovskite WG laser can be significantly decreased to a few hundred nanometers. Thus, wavelength-scale lead halide perovskite lasers were realized for the first time. All of these laser behaviors are complementary to typical random lasers in perovskite film and will help the understanding of lasing actions in complex lead halide perovskite systems.

Progress of the volume FEL (VFEL) experiments in millimeter range

NASA Astrophysics Data System (ADS)

Baryshevsky, V. G.; Batrakov, K. G.; Gurinovich, A. A.; Ilienko, I. I.; Lobko, A. S.; Molchanov, P. V.; Moroz, V. I.; Sofronov, P. F.; Stolyarsky, V. I.

2003-07-01

Use of non-one-dimensional distributed feedback in Volume Free Electron Laser gives possibility of frequency tuning in wide range. In present work, dependence of lasing process on the angle between resonant diffraction grating grooves and direction of electron beam velocity is discussed.

Growth and lasing of single crystal YAG fibers with different Ho3+ concentrations

NASA Astrophysics Data System (ADS)

Bera, Subhabrata; Nie, Craig D.; Soskind, Michael G.; Li, Yuan; Harrington, James A.; Johnson, Eric G.

2018-01-01

A method to grow single crystal (SC) yttrium aluminum garnet (YAG) fibers with varied rare-earth ion dopant concentration has been proposed. Crystalline holmium aluminum garnet (HoAG), prepared via sol-gel process, was dip-coated on to previously grown SC YAG fibers. The HoAG coated SC YAG fiber preforms were re-grown to a smaller diameter using the laser heated pedestal growth (LHPG) technique. The final dopant concentration of the re-grown SC fiber was varied by changing the number of HoAG coatings on the preform. 120 μm diameter SC Ho:YAG fibers with four different dopant concentrations were grown. Lasing was demonstrated at 2.09 μm for these fibers. A maximum of 58.5% optical-to-optical slope efficiency was obtained.

Ultrafast Pulse Generation in an Organic Nanoparticle-Array Laser.

PubMed

Daskalakis, Konstantinos S; Väkeväinen, Aaro I; Martikainen, Jani-Petri; Hakala, Tommi K; Törmä, Päivi

2018-04-11

Nanoscale coherent light sources offer potentially ultrafast modulation speeds, which could be utilized for novel sensors and optical switches. Plasmonic periodic structures combined with organic gain materials have emerged as promising candidates for such nanolasers. Their plasmonic component provides high intensity and ultrafast nanoscale-confined electric fields, while organic gain materials offer fabrication flexibility and a low acquisition cost. Despite reports on lasing in plasmonic arrays, lasing dynamics in these structures have not been experimentally studied yet. Here we demonstrate, for the first time, an organic dye nanoparticle-array laser with more than a 100 GHz modulation bandwidth. We show that the lasing modulation speed can be tuned by the array parameters. Accelerated dynamics is observed for plasmonic lasing modes at the blue side of the dye emission.

Fiber-Type Random Laser Based on a Cylindrical Waveguide with a Disordered Cladding Layer.

PubMed

Zhang, Wei Li; Zheng, Meng Ya; Ma, Rui; Gong, Chao Yang; Yang, Zhao Ji; Peng, Gang Ding; Rao, Yun Jiang

2016-05-25

This letter reports a fiber-type random laser (RL) which is made from a capillary coated with a disordered layer at its internal surface and filled with a gain (laser dye) solution in the core region. This fiber-type optical structure, with the disordered layer providing randomly scattered light into the gain region and the cylindrical waveguide providing confinement of light, assists the formation of random lasing modes and enables a flexible and efficient way of making random lasers. We found that the RL is sensitive to laser dye concentration in the core region and there exists a fine exponential relationship between the lasing intensity and particle concentration in the gain solution. The proposed structure could be a fine platform of realizing random lasing and random lasing based sensing.

The Effect of an Instructional Intervention on Enhancement Pre-Service Science Teachers' Science Processes Skills

ERIC Educational Resources Information Center

Durmaz, Hüsnüye

2016-01-01

The aim of this study is to investigate the effects of an instructional intervention on enhancement the pre-service science teachers' (PSTs) science process skills (SPSs) and to identify problems in using SPSs through Laboratory Applications in Science Education-I course (LASE-I). One group pretest-posttest pre-experimental design was employed. An…

Method and apparatus for tuning high power lasers

DOEpatents

Hutchinson, Donald P.; Vandersluis, Kenneth L.

1977-04-19

This invention relates to high power gas lasers that are adapted to be tuned to a desired lasing wavelength through the use of a gas cell to lower the gain at a natural lasing wavelength and "seeding" the laser with a beam from a low power laser which is lasing at the desired wavelength. This tuning is accomplished with no loss of power and produces a pulse with an altered pulse shape. It is potentially applicable to all gas lasers.

Robust Subwavelength Single-Mode Perovskite Nanocuboid Laser.

PubMed

Liu, Zhengzheng; Yang, Jie; Du, Juan; Hu, Zhiping; Shi, Tongchao; Zhang, Zeyu; Liu, Yanqi; Tang, Xiaosheng; Leng, Yuxin; Li, Ruxin

2018-05-14

On-chip photonic information processing systems require great research efforts toward miniaturization of the optical components. However, when approaching the classical diffraction limit, conventional dielectric lasers with all dimensions in nanoscale are difficult to realize due to the ultimate miniaturization limit of the cavity length and the extremely high requirement of optical gain to overcome the cavity loss. Herein, we have succeeded in reducing the laser size to subwavelength scale in three dimensions using an individual CsPbBr 3 perovskite nanocuboid. Even though the side length of the nanocuboid laser is only ∼400 nm, single-mode Fabry-Pérot lasing at room temperature with laser thresholds of 40.2 and 374 μJ/cm 2 for one- and two-photon excitation has been achieved, respectively, with the corresponding quality factors of 2075 and 1859. In addition, temperature-insensitive properties from 180 to 380 K have been demonstrated. The physical volume of a CsPbBr 3 nanocuboid laser is only ∼0.49λ 3 (where λ is the lasing wavelength in air). Its three-dimensional subwavelength size, excellent stable lasing performance at room temperature, frequency up-conversion ability, and temperature-insensitive properties may lead to a miniaturized platform for nanolasers and integrated on-chip photonic devices in nanoscale.

Stability of quantum-dot excited-state laser emission under simultaneous ground-state perturbation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaptan, Y., E-mail: yuecel.kaptan@physik.tu-berlin.de; Herzog, B.; Schöps, O.

2014-11-10

The impact of ground state amplification on the laser emission of In(Ga)As quantum dot excited state lasers is studied in time-resolved experiments. We find that a depopulation of the quantum dot ground state is followed by a drop in excited state lasing intensity. The magnitude of the drop is strongly dependent on the wavelength of the depletion pulse and the applied injection current. Numerical simulations based on laser rate equations reproduce the experimental results and explain the wavelength dependence by the different dynamics in lasing and non-lasing sub-ensembles within the inhomogeneously broadened quantum dots. At high injection levels, the observedmore » response even upon perturbation of the lasing sub-ensemble is small and followed by a fast recovery, thus supporting the capacity of fast modulation in dual-state devices.« less

Mode selection in square resonator microlasers for widely tunable single mode lasing.

PubMed

Tang, Ming-Ying; Sui, Shao-Shuai; Yang, Yue-De; Xiao, Jin-Long; Du, Yun; Huang, Yong-Zhen

2015-10-19

Mode selection in square resonator semiconductor microlasers is demonstrated by adjusting the width of the output waveguide coupled to the midpoint of one side. The simulation and experimental results reveal that widely tunable single mode lasing can be realized in square resonator microlasers. Through adjusting the width of the output waveguide, the mode interval of the high-Q modes can reach four times of the longitudinal mode interval. Therefore, mode hopping can be efficiently avoided and the lasing wavelength can be tuned continuously by tuning the injection current. For a 17.8-μm-side-length square microlaser with a 1.4-μm-width output waveguide, mode-hopping-free single-mode operation is achieved with a continuous tuning range of 9.2 nm. As a result, the control of the lasing mode is realized for the square microlasers.

Versatile tissue lasers based on high-Q Fabry-Pérot microcavities.

PubMed

Chen, Yu-Cheng; Chen, Qiushu; Zhang, Tingting; Wang, Wenjie; Fan, Xudong

2017-01-31

Biolasers are an emerging technology for next generation biochemical detection and clinical applications. Progress has recently been made to achieve lasing from biomolecules and single living cells. Tissues, which consist of cells embedded in an extracellular matrix, mimic more closely the actual complex biological environment in a living body and therefore are of more practical significance. Here, we developed a highly versatile tissue laser platform, in which tissues stained with fluorophores are sandwiched in a high-Q Fabry-Pérot microcavity. Distinct lasing emissions from muscle and adipose tissues stained respectively with fluorescein isothiocyanate (FITC) and boron-dipyrromethene (BODIPY), and hybrid muscle/adipose tissue with dual staining were achieved with a threshold of only ∼10 μJ mm -2 . Additionally, we investigated how the tissue structure/geometry, tissue thickness, and staining dye concentration affect the tissue laser. Lasing emission from FITC conjugates (FITC-phalloidin) that specifically target F-actin in muscle tissues was also realized. It is further found that, despite the large fluorescence spectral overlap between FITC and BODIPY in tissues, their lasing emissions could be clearly distinguished and controlled due to their narrow lasing bands and different lasing thresholds, thus enabling highly multiplexed detection. Our tissue laser platform can be broadly applicable to various types of tissues/diseases. It provides a new tool for a wide range of biological and biomedical applications, such as diagnostics/screening of tissues and identification/monitoring of biological transformations in tissue engineering.

Switching of Photonic Crystal Lasers by Graphene.

PubMed

Hwang, Min-Soo; Kim, Ha-Reem; Kim, Kyoung-Ho; Jeong, Kwang-Yong; Park, Jin-Sung; Choi, Jae-Hyuck; Kang, Ju-Hyung; Lee, Jung Min; Park, Won Il; Song, Jung-Hwan; Seo, Min-Kyo; Park, Hong-Gyu

2017-03-08

Unique features of graphene have motivated the development of graphene-integrated photonic devices. In particular, the electrical tunability of graphene loss enables high-speed modulation of light and tuning of cavity resonances in graphene-integrated waveguides and cavities. However, efficient control of light emission such as lasing, using graphene, remains a challenge. In this work, we demonstrate on/off switching of single- and double-cavity photonic crystal lasers by electrical gating of a monolayer graphene sheet on top of photonic crystal cavities. The optical loss of graphene was controlled by varying the gate voltage V g , with the ion gel atop the graphene sheet. First, the fundamental properties of graphene were investigated through the transmittance measurement and numerical simulations. Next, optically pumped lasing was demonstrated for a graphene-integrated single photonic crystal cavity at V g below -0.6 V, exhibiting a low lasing threshold of ∼480 μW, whereas lasing was not observed at V g above -0.6 V owing to the intrinsic optical loss of graphene. Changing quality factor of the graphene-integrated photonic crystal cavity enables or disables the lasing operation. Moreover, in the double-cavity photonic crystal lasers with graphene, switching of individual cavities with separate graphene sheets was achieved, and these two lasing actions were controlled independently despite the close distance of ∼2.2 μm between adjacent cavities. We believe that our simple and practical approach for switching in graphene-integrated active photonic devices will pave the way toward designing high-contrast and ultracompact photonic integrated circuits.

Controlling the gain contribution of background emitters in few-quantum-dot microlasers

NASA Astrophysics Data System (ADS)

Gericke, F.; Segnon, M.; von Helversen, M.; Hopfmann, C.; Heindel, T.; Schneider, C.; Höfling, S.; Kamp, M.; Musiał, A.; Porte, X.; Gies, C.; Reitzenstein, S.

2018-02-01

We provide experimental and theoretical insight into single-emitter lasing effects in a quantum dot (QD)-microlaser under controlled variation of background gain provided by off-resonant discrete gain centers. For that purpose, we apply an advanced two-color excitation concept where the background gain contribution of off-resonant QDs can be continuously tuned by precisely balancing the relative excitation power of two lasers emitting at different wavelengths. In this way, by selectively exciting a single resonant QD and off-resonant QDs, we identify distinct single-QD signatures in the lasing characteristics and distinguish between gain contributions of a single resonant emitter and a countable number of off-resonant background emitters to the optical output of the microlaser. Our work addresses the important question whether single-QD lasing is feasible in experimentally accessible systems and shows that, for the investigated microlaser, the single-QD gain needs to be supported by the background gain contribution of off-resonant QDs to reach the transition to lasing. Interestingly, while a single QD cannot drive the investigated micropillar into lasing, its relative contribution to the emission can be as high as 70% and it dominates the statistics of emitted photons in the intermediate excitation regime below threshold.

Investigation of Material Gain of In0.90Ga0.10As0.59P0.41/InP Lasing Nano-Heregostructure

NASA Astrophysics Data System (ADS)

Yadav, Rashmi; Lal, Pyare; Rahman, F.; Dalela, S.; Alvi, P. A.

2014-02-01

In this paper, we have proposed a step separate confinement heterostructure (SCH) based lasing nano-heterostructure In0.90Ga0.10As0.59P0.41/InP consisting of single quantum well (SQW) and investigated material gain theoretically within TE and TM polarization modes. In addition, the quasi Fermi levels in the conduction and valence bands along with other lasing characteristics like anti-guiding factor, refractive index change with carrier density and differential gain have also been investigated and reported. Moreover, the behavior of quasi Fermi levels in respective bands has also been correlated with the material gain. Strain dependent study on material gain and refractive index change has also been reported. Interestingly, strain has been reported to play a very important role in shifting the lasing wavelength of TE mode to TM mode. The results investigated in the work suggest that the proposed unstrained nano-heterostructure is very suitable as a source for optical fiber based communication systems due to its lasing wavelengths achieved at 1.35 μm within TM mode, while 1.40 μm within TE mode.

Lasing in robust cesium lead halide perovskite nanowires

PubMed Central

Eaton, Samuel W.; Lai, Minliang; Gibson, Natalie A.; Wong, Andrew B.; Dou, Letian; Ma, Jie; Wang, Lin-Wang; Leone, Stephen R.; Yang, Peidong

2016-01-01

The rapidly growing field of nanoscale lasers can be advanced through the discovery of new, tunable light sources. The emission wavelength tunability demonstrated in perovskite materials is an attractive property for nanoscale lasers. Whereas organic–inorganic lead halide perovskite materials are known for their instability, cesium lead halides offer a robust alternative without sacrificing emission tunability or ease of synthesis. Here, we report the low-temperature, solution-phase growth of cesium lead halide nanowires exhibiting low-threshold lasing and high stability. The as-grown nanowires are single crystalline with well-formed facets, and act as high-quality laser cavities. The nanowires display excellent stability while stored and handled under ambient conditions over the course of weeks. Upon optical excitation, Fabry–Pérot lasing occurs in CsPbBr3 nanowires with an onset of 5 μJ cm−2 with the nanowire cavity displaying a maximum quality factor of 1,009 ± 5. Lasing under constant, pulsed excitation can be maintained for over 1 h, the equivalent of 109 excitation cycles, and lasing persists upon exposure to ambient atmosphere. Wavelength tunability in the green and blue regions of the spectrum in conjunction with excellent stability makes these nanowire lasers attractive for device fabrication. PMID:26862172

Random lasing actions in self-assembled perovskite nanoparticles

NASA Astrophysics Data System (ADS)

Liu, Shuai; Sun, Wenzhao; Li, Jiankai; Gu, Zhiyuan; Wang, Kaiyang; Xiao, Shumin; Song, Qinghai

2016-05-01

Solution-based perovskite nanoparticles have been intensively studied in the past few years due to their applications in both photovoltaic and optoelectronic devices. Here, based on the common ground between solution-based perovskite and random lasers, we have studied the mirrorless lasing actions in self-assembled perovskite nanoparticles. After synthesis from a solution, discrete lasing peaks have been observed from optically pumped perovskites without any well-defined cavity boundaries. We have demonstrated that the origin of the random lasing emissions is the scattering between the nanostructures in the perovskite microplates. The obtained quality (Q) factors and thresholds of random lasers are around 500 and 60 μJ/cm2, respectively. Both values are comparable to the conventional perovskite microdisk lasers with polygon-shaped cavity boundaries. From the corresponding studies on laser spectra and fluorescence microscope images, the lasing actions are considered random lasers that are generated by strong multiple scattering in random gain media. In additional to conventional single-photon excitation, due to the strong nonlinear effects of perovskites, two-photon pumped random lasers have also been demonstrated for the first time. We believe this research will find its potential applications in low-cost coherent light sources and biomedical detection.

The analytical approach to the multi-state lasing phenomenon in undoped and p-doped InAs/InGaAs semiconductor quantum dot lasers

NASA Astrophysics Data System (ADS)

Korenev, Vladimir V.; Savelyev, Artem V.; Zhukov, Alexey E.; Omelchenko, Alexander V.; Maximov, Mikhail V.

2014-05-01

We introduce an analytical approach to the multi-state lasing phenomenon in p-doped and undoped InAs/InGaAs quantum dot lasers which were studied both theoretically and experimentally. It is shown that the asymmetry in charge carrier distribution in quantum dots as well as hole-to-electron capture rate ratio jointly determine laser's behavior in such a regime. If the ratio is lower than a certain critical value, the complete quenching of ground-state lasing takes place at sufficiently high injection currents; at higher values of the ratio, our model predicts saturation of the ground-state power. It was experimentally shown that the modulation p-doping of laser's active region results in increase of output power emitted via the ground-state optical transitions of quantum dots and in enhancement of the injection currents range in which multi-state lasing takes place. The maximum temperature at which multi-state lasing exists was increased by about 50°C in the p-doped samples. These effects are qualitatively explained in the terms of the proposed model.

Composition-Graded Cesium Lead Halide Perovskite Nanowires with Tunable Dual-Color Lasing Performance.

PubMed

Huang, Ling; Gao, Qinggang; Sun, Ling-Dong; Dong, Hao; Shi, Shuo; Cai, Tong; Liao, Qing; Yan, Chun-Hua

2018-05-21

Cesium lead halide (CsPbX 3 ) perovskite has emerged as a promising low-threshold multicolor laser material; however, realizing wavelength-tunable lasing output from a single CsPbX 3 nanostructure is still constrained by integrating different composition. Here, the direct synthesis of composition-graded CsPbBr x I 3- x nanowires (NWs) is reported through vapor-phase epitaxial growth on mica. The graded composition along the NW, with an increased Br/I from the center to the ends, comes from desynchronized deposition of cesium lead halides and temperature-controlled anion-exchange reaction. The graded composition results in varied bandgaps along the NW, which induce a blueshifted emission from the center to the ends. As an efficient gain media, the nanowire exerts position-dependent lasing performance, with a different color at the ends and center respectively above the threshold. Meanwhile, dual-color lasing with a wavelength separation of 35 nm is activated simultaneously at a site with an intermediate composition. This position-dependent dual-color lasing from a single nanowire makes these metal halide perovskites promising for applications in nanoscale optical devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

XeCl Avalanche discharge laser employing Ar as a diluent

DOEpatents

Sze, Robert C.

1981-01-01

A XeCl avalanche discharge exciplex laser which uses a gaseous lasing starting mixture of: (0.2%-0.4% chlorine donor/2.5%-10% Xe/97.3%-89.6% Ar). The chlorine donor normally comprises HCl but can also comprise CCl.sub.4 BCl.sub.3. Use of Ar as a diluent gas reduces operating pressures over other rare gas halide lasers to near atmospheric pressure, increases output lasing power of the XeCl avalanche discharge laser by 30% to exceed KrF avalanche discharge lasing outputs, and is less expensive to operate.

Mie resonances to tailor random lasers

NASA Astrophysics Data System (ADS)

García, P. D.; Ibisate, M.; Sapienza, R.; Wiersma, D. S.; López, C.

2009-07-01

In this paper, we present an optical characterization of photonic glass-based random lasers. We show how the resonant behavior of diffuse light transport through such systems can tailor the lasing emission when a gain medium is added to the glass. A DNA-based organic dye is used as gain medium. The resonances in the transport mean-free path influence the lasing wavelength of the random laser. The laser wavelength is therefore controlled by the sphere diameter. Furthermore, the existence of Mie resonances reduces the necessary pump energy to reach the lasing threshold.

Multiwavelength ultralow-threshold lasing in quantum dot photonic crystal microcavities.

PubMed

Chakravarty, S; Bhattacharya, P; Chakrabarti, S; Mi, Z

2007-05-15

We demonstrate multiwavelength lasing of resonant modes in linear (L3) microcavities in a triangular-lattice 2D photonic crystal (PC) slab. The broad spontaneous emission spectrum from coupled quantum dots, modified by the PC microcavity, is studied as a function of the intensity of incident optical excitation. We observe lasing with an ultralow-threshold power of approximately 600 nW and an output efficiency of approximately 3% at threshold. Two other resonant modes exhibit weaker turnon characteristics and thresholds of approximately 2.5 and 200 microW, respectively.

Dual-wavelength single-frequency laser emission in asymmetric coupled microdisks

PubMed Central

Wang, Haotian; Liu, Sheng; Chen, Lin; Shen, Deyuan; Wu, Xiang

2016-01-01

The gain and loss in a microcavity laser play an important role for the modulation of laser spectrum. We show that dual-wavelength single mode lasing can be achieved in an asymmetric coupled system consisted of two size-mismatched microdisks. The amount of eigenmodes in this coupled-microdisk system is reduced relying on the Vernier effect. Then a single mode is selected to lase by controlling the gain branching in the supermodes. The supermodes are formed by the coupling between different transverse whispering-gallery modes (WGMs). When the gain/loss status between the two mirodisks is changed through selectively pumping process, the modulated gain branching for various supermodes leads to the switchable single-frequency laser emission. The results obtained in this work will provide the further understand for the spectral modulation mechanism in the coupled microcavity laser system. PMID:27905506

Evaluation of sub-surface penetration and bonding durability of self-etching primer systems to Er:YAG laser treated cervical dentin.

PubMed

He, Zhengdi; Chen, Lingling; Shimada, Yasushi; Tagami, Junji; Ruan, Shuangchen

2017-03-31

This study aimed to investigate self-etching bonding systems penetrating in sub-surface dentin layer after Er:YAG laser irradiation and micro-shear bonding durability over a period of 1 year. Dentin slices obtained from extracted human third molars were prepared. Two self-etching adhesive systems were evaluated: Clearfil SE Bond and Clearfil Tri-S Bond. Specimens were tested for micro-shear bond strength with one of the following treatments: Er:YAG laser irradiation and 600-grit silicon paper polishing at 24 h, 7 days, 6 months and 1 year. The adhesive interfaces between bonding agents and lased cervical dentin were studied. No hybrid layer could be observed for lased dentin. The slim resin tags could be seen penetrating through the lased subsurface layer. Bond strength to lased dentin after 6 months and 1 year were significantly decreased (p<0.05).

Amplified emission and lasing in a plasmonic nanolaser with many three-level molecules

NASA Astrophysics Data System (ADS)

Zhang, Yuan; Mølmer, Klaus

2018-01-01

Steady-state plasmonic lasing is studied theoretically for a system consisting of many dye molecules arranged regularly around a gold nanosphere. A three-level model with realistic molecular dissipation is employed to analyze the performance as a function of the pump field amplitude and number of molecules. Few molecules and moderate pumping produce a single narrow emission peak because the excited molecules transfer energy to a single dipole plasmon mode by amplified spontaneous emission. Under strong pumping, the single peak splits into broader and weaker emission peaks because two molecular excited levels interfere with each other through coherent coupling with the pump field and with the dipole plasmon field. A large number of molecules gives rise to a Poisson-like distribution of plasmon number states with a large mean number characteristic of lasing action. These characteristics of lasing, however, deteriorate under strong pumping because of the molecular interference effect.

Lasing from lead halide perovskite semiconductor microcavity system.

PubMed

Wang, Jun; Da, Peimei; Zhang, Zhe; Luo, Song; Liao, Liming; Sun, Zeyuan; Shen, Xuechu; Wu, Shiwei; Zheng, Gengfeng; Chen, Zhanghai

2018-06-07

Organic-inorganic halide perovskite semiconductors are ideal gain media for fabricating laser and photonic devices due to high absorption, photoluminescence (PL) efficiency and low nonradiative recombination losses. Herein, organic-inorganic halide perovskite CH3NH3PbI3 is embedded in the Fabry-Perot (FP) microcavity, and a wavelength-tunable excitonic lasing with a threshold of 12.9 μJ cm-2 and the spectral coherence of 0.76 nm are realized. The lasing threshold decreases and the spectral coherence enhances as the temperature decreases; these results are ascribed to the suppression of exciton irradiative recombination caused by thermal fluctuation. Moreover, both lasing and light emission below threshold from the perovskite microcavity (PM) system demonstrate a redshift with the decreasing temperature. These results provide a feasible platform based on the PM system for the study of light-matter interaction for quantum optics and the development of optoelectronic devices such as polariton lasers.

LASE Observations of Interactions Between African Easterly Waves and the Saharan Air Layer

NASA Technical Reports Server (NTRS)

Ismail, Syed; Ferrare, Richard; Browell, Edward; Kooi, Susan; Biswas, Mrinal; Krishnamurti, T. N.; Notari, Anthony; Heymsfield, Andrew; Butler, Carolyn; Burton, Sharon;

The effects of cooling systems on CO2-lased human enamel.

PubMed

Lian, H J; Lan, W H; Lin, C P

1996-12-01

The thermal effects on dentin during CO2 laser irradiation on human enamel were investigated. To simulate the clinical practice, two cooling methods (air and water spray) were applied immediately after laser exposure, whereas one group without cooling was served as control. Three hundred and sixty uniform tooth blocks were obtained from freshly extracted human third molars. Temperature change measurements were made via electrical thermocouple implanted within the tooth block 2 mm away from the enamel surface. Experimental treatments consisted of lasing without cooling, lasing with 0.5-ml/sec water cooling, and lasing with 15-psi air cooling. Our results indicated that (1) both air- and water-cooling groups could reduce temperature elevation significantly; (2) the larger power energy resulted in the higher temperature elevation. In conclusion, for CO2 laser irradiation on human enamel both water- and air-cooling methods may be effective on prevention of thermal damage of pulp.

Photophysical and lasing properties of new analogs of the boron-dipyrromethene laser dye pyrromethene 567 incorporated into or covalently bounded to solid matrices of poly(methyl methacrylate).

PubMed

López Arbeloa, F; Bañuelos Prieto, J; López Arbeloa, I; Costela, A; García-Moreno, I; Gómez, C; Amat-Guerri, F; Liras, M; Sastre, R

2003-07-01

The photophysical, lasing and thermostability properties of newly synthesized analogs of the commercial dye pyrromethene 567 (PM567) have been measured in polymeric matrices of poly(methyl methacrylate) both when used as a dopant and when covalently bounded to the polymeric chain. These analogs have an acetoxy or a polymerizable methacryloyloxy group at the end of a polymethylene chain at Position 8 of the PM567 chromophore core. Clear correlations between photophysical and lasing characteristics are observed. Linking chain lengths with three or more methylene units give the highest fluorescence quantum yields (as high as 0.89) and lasing efficiencies (as high as 41%). The covalent linkage of the chromophore to the polymeric chain via the methacryloyloxy group improves the photostability of the PM567 chromophore.

Laser systems configured to output a spectrally-consolidated laser beam and related methods

DOEpatents

Koplow, Jeffrey P [San Ramon, CA

2012-01-10

A laser apparatus includes a plurality of pumps each of which is configured to emit a corresponding pump laser beam having a unique peak wavelength. The laser apparatus includes a spectral beam combiner configured to combine the corresponding pump laser beams into a substantially spatially-coherent pump laser beam having a pump spectrum that includes the unique peak wavelengths, and first and second selectively reflective elements spaced from each other to define a lasing cavity including a lasing medium therein. The lasing medium generates a plurality of gain spectra responsive to absorbing the pump laser beam. Each gain spectrum corresponds to a respective one of the unique peak wavelengths of the substantially spatially-coherent pump laser beam and partially overlaps with all other ones of the gain spectra. The reflective elements are configured to promote emission of a laser beam from the lasing medium with a peak wavelength common to each gain spectrum.

Analysis of lasers as a solution to efficiency droop in solid-state lighting

DOE PAGES

Chow, Weng W.; Crawford, Mary H.

2015-10-06

This letter analyzes the proposal to mitigate the efficiency droop in solid-state light emitters by replacing InGaN light-emitting diodes (LEDs) with lasers. The argument in favor of this approach is that carrier-population clamping after the onset of lasing limits carrier loss to that at threshold, while stimulated emission continues to grow with injection current. A fully quantized (carriers and light) theory that is applicable to LEDs and lasers (above and below threshold) is used to obtain a quantitative evaluation. The results confirm the potential advantage of higher laser output power and efficiency above lasing threshold, while also indicating disadvantages includingmore » low efficiency prior to lasing onset, sensitivity of lasing threshold to temperature, and the effects of catastrophic laser failure. As a result, a solution to some of these concerns is suggested that takes advantage of recent developments in nanolasers.« less

Thermally and optically tunable lasing properties from dye-doped holographic polymer dispersed liquid crystal in capillaries

NASA Astrophysics Data System (ADS)

Chen, Maozhou; Dai, Haitao; Wang, Dongshuo; Yang, Yue; Luo, Dan; Zhang, Xiaodong; Liu, Changlong

2018-03-01

In this paper, we investigated tunable lasing properties from the dye-doped holographic polymer dispersed liquid crystal (HPDLC) gratings in capillaries with thermal and optical manners. The thermally tunable range of the lasing from the dye-doped HPDLC reached 8.60 nm with the temperature ranging from 23 °C to 50 °C. The optically tunable laser emission was achieved by doping azo-dye in HPDLC. The transition of azo-dye from trans- to cis-state could induce the reorientation of LC molecules after UV light irradiation, which resulted in the variation of refractive index contrast of LC-rich/polymer-rich layer in HPDLC. Experimentally, the emission wavelength of lasing showed a blueshift (about 2 nm) coupled with decreasing output intensities. The tunable laser based on HPDLC may enable more applications in laser displays, optical communication, biosensors, etc.

Cleaved-coupled nanowire lasers

PubMed Central

Gao, Hanwei; Fu, Anthony; Andrews, Sean C.; Yang, Peidong

2013-01-01

The miniaturization of optoelectronic devices is essential for the continued success of photonic technologies. Nanowires have been identified as potential building blocks that mimic conventional photonic components such as interconnects, waveguides, and optical cavities at the nanoscale. Semiconductor nanowires with high optical gain offer promising solutions for lasers with small footprints and low power consumption. Although much effort has been directed toward controlling their size, shape, and composition, most nanowire lasers currently suffer from emitting at multiple frequencies simultaneously, arising from the longitudinal modes native to simple Fabry–Pérot cavities. Cleaved-coupled cavities, two Fabry–Pérot cavities that are axially coupled through an air gap, are a promising architecture to produce single-frequency emission. The miniaturization of this concept, however, imposes a restriction on the dimensions of the intercavity gaps because severe optical losses are incurred when the cross-sectional dimensions of cavities become comparable to the lasing wavelength. Here we theoretically investigate and experimentally demonstrate spectral manipulation of lasing modes by creating cleaved-coupled cavities in gallium nitride (GaN) nanowires. Lasing operation at a single UV wavelength at room temperature was achieved using nanoscale gaps to create the smallest cleaved-coupled cavities to date. Besides the reduced number of lasing modes, the cleaved-coupled nanowires also operate with a lower threshold gain than that of the individual component nanowires. Good agreement was found between the measured lasing spectra and the predicted spectral modes obtained by simulating optical coupling properties. This agreement between theory and experiment presents design principles to rationally control the lasing modes in cleaved-coupled nanowire lasers. PMID:23284173

Solar pumped laser

NASA Technical Reports Server (NTRS)

Lee, J. H.; Hohl, F.; Weaver, W. R. (Inventor)

1984-01-01

A solar pumped laser is described in which the lasant is a gas that will photodissociate and lase when subjected to sunrays. Sunrays are collected and directed onto the gas lasant to cause it to lase. Applications to laser propulsion and laser power transmission are discussed.

Rainbow glare by retinal imaging

NASA Astrophysics Data System (ADS)

Sun, Han-Ying; Chiang, Yao-Ting; Yeh, Shang-Min; Huang, Shuan-Yu; Horng, Chi-Ting; Wang, Hsiang-Chen

2016-07-01

This study aims to determine whether IntraLase surgery can cause rainbow glare. Monte-Carlo ray tracing method is used to study visual conditions of an ordered microstructure array on the cornea. A corneal flap in the simulated eye model can generate numerous microbubbles caused by IntraLase surgery. Moreover, this study evaluates the visual performance under different conditions such as the size and interval of the microbubble structure on the cornea with vary incident angles and diameters of light. The results of this study can help elucidate the real cause of rainbow glare as a side effect of IntraLase.

Frequency combs with weakly lasing exciton-polariton condensates.

PubMed

Rayanov, K; Altshuler, B L; Rubo, Y G; Flach, S

2015-05-15

We predict the spontaneous modulated emission from a pair of exciton-polariton condensates due to coherent (Josephson) and dissipative coupling. We show that strong polariton-polariton interaction generates complex dynamics in the weak-lasing domain way beyond Hopf bifurcations. As a result, the exciton-polariton condensates exhibit self-induced oscillations and emit an equidistant frequency comb light spectrum. A plethora of possible emission spectra with asymmetric peak distributions appears due to spontaneously broken time-reversal symmetry. The lasing dynamics is affected by the shot noise arising from the influx of polaritons. That results in a complex inhomogeneous line broadening.

Lasing of multiperiod quantum-cascade lasers in the spectral range of (5.6–5.8)-μm under current pumping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Egorov, A. Yu., E-mail: anton@beam.ioffe.ru; Babichev, A. V.; Karachinsky, L. Ya.

2015-11-15

The lasing of multiperiod quantum-cascade lasers in the spectral range of (5.6–5.8)-μm under current pumping are demonstrated. The quantum-cascade laser heterostructure is grown by molecular-beam epitaxy technique. Despite the relatively short laser cavity length and high level of external loss the laser shows the lasing in the temperature range of 80–220 K. The threshold current density below 4 kA/cm{sup 2} at 220 K with the characteristic temperature T{sub 0} = 123 K was demonstrated.

XeCl avalanche discharge laser employing Ar as a diluent

DOEpatents

Sze, R.C.

1979-10-10

A XeCl avalanche discharge exciplex laser which uses a gaseous lasing starting mixture of: 0.2 to 0.4% chlorine donor/2.5% to 10% Xe/97.3% to 89.6% Ar) is provided. The chlorine donor normally comprises HCl but can also comprise CCl/sub 4/ BCl/sub 3/. Use of Ar as a diluent gas reduces operating pressures over other rare gas halide lasers to near atmospheric pressure, increases output lasing power of the XeCl avalanche discharge laser by 30% to exceed KrF avalanche discharge lasing outputs, and is less expensive to operate.

Room-Temperature Low-Threshold Lasing from Monolithically Integrated Nanostructured Porous Silicon Hybrid Microcavities.

PubMed

Robbiano, Valentina; Paternò, Giuseppe M; La Mattina, Antonino A; Motti, Silvia G; Lanzani, Guglielmo; Scotognella, Francesco; Barillaro, Giuseppe

2018-05-22

Silicon photonics would strongly benefit from monolithically integrated low-threshold silicon-based laser operating at room temperature, representing today the main challenge toward low-cost and power-efficient electronic-photonic integrated circuits. Here we demonstrate low-threshold lasing from fully transparent nanostructured porous silicon (PSi) monolithic microcavities (MCs) infiltrated with a polyfluorene derivative, namely, poly(9,9-di- n-octylfluorenyl-2,7-diyl) (PFO). The PFO-infiltrated PSiMCs support single-mode blue lasing at the resonance wavelength of 466 nm, with a line width of ∼1.3 nm and lasing threshold of 5 nJ (15 μJ/cm 2 ), a value that is at the state of the art of PFO lasers. Furthermore, time-resolved photoluminescence shows a significant shortening (∼57%) of PFO emission lifetime in the PSiMCs, with respect to nonresonant PSi reference structures, confirming a dramatic variation of the radiative decay rate due to a Purcell effect. Our results, given also that blue lasing is a worst case for silicon photonics, are highly appealing for the development of low-cost, low-threshold silicon-based lasers with wavelengths tunable from visible to the near-infrared region by simple infiltration of suitable emitting polymers in monolithically integrated nanostructured PSiMCs.

CW 3μm lasing via two-photon pumping in cesium vapor with a 1W source

NASA Astrophysics Data System (ADS)

Haluska, Nathan D.; Rice, Christopher A.; Perram, Glen P.

2018-02-01

We report the first CW lasing from two-photon pumping via a virtual state. Pulsed and the CW lasing of the 3096 nm 72 P1/2 to 72 S1/2 line are observed from degenerate two-photon pumping of the cesium 72 S1/2 to 62 D3/2 transition. High intensity pulses excite over 17 lasing wavelengths. Under lower intensity CW excitation, 3 μm lasing is still observed with efficiencies of 0.7%. CW experiments utilized a Cs heat pipe at 150 °C to 270 °C, and a highly-focused, single pass, Ti-Sapphire pump with no aid of a cavity. Unlike normal DPALS, this architecture does not require buffer gas, and heat is released optically so a flowing system is not required. Both suggest a very simple device with excellent beam quality is possible. This proof of concept can be greatly enhanced with more optimal conditions such as non-degenerate pumping to further increase the two-photon pump cross section and the addition of a cavity to improve mode volume overlap. These improvements may lead to an increase in efficiencies to a theoretical maximum of 14%. Results suggest two-photon pumping with diodes is feasible.

Evaluation of primary tooth enamel surface morphology and microhardness after Nd:YAG laser irradiation and APF gel treatment--an in vitro study.

PubMed

Banda, Naveen Reddy; Vanaja Reddy, G; Shashikiran, N D

2011-01-01

Laser irradiation and fluoride has been used as a preventive tool to combat dental caries in permanent teeth, but little has been done for primary teeth which are more prone to caries. The purpose of this study was to evaluate microhardness alterations in the primary tooth enamel after Nd-YAG laser irradiation alone and combined with topical fluoride treatment either before or after Nd-YAG laser irradiation. Ten primary molars were sectioned and assigned randomly to: control group, Nd-YAG laser irradiation, Nd-YAG lasing before APF and APF followed by Nd-YAG lasing. The groups were evaluated for microhardness. Surface morphological changes were observed using SEM. Statistical comparisons were performed. The control group's SEM showed a relatively smooth enamel surface and lasing group had fine cracks and porosities. In the lasing + fluoride group a homogenous confluent surface was seen. In the fluoride + lasing group an irregular contour with marked crack propagation was noted. There was a significant increase in the microhardness of the treatment groups. Nd-YAG laser irradiation and combined APF treatment of the primary tooth enamel gave morphologically hardened enamel surface which can be a protective barrier against a cariogenic attack.

Lasing in robust cesium lead halide perovskite nanowires

DOE PAGES

Eaton, Samuel W.; Lai, Minliang; Gibson, Natalie A.; ...

2016-02-09

The rapidly growing field of nanoscale lasers can be advanced through the discovery of new, tunable light sources. The emission wavelength tunability demonstrated in perovskite materials is an attractive property for nanoscale lasers. Whereas organic-inorganic lead halide perovskite materials are known for their instability, cesium lead halides offer a robust alternative without sacrificing emission tunability or ease of synthesis. Here, we report the low-temperature, solution-phase growth of cesium lead halide nanowires exhibiting low-threshold lasing and high stability. The as-grown nanowires are single crystalline with well-formed facets, and act as high-quality laser cavities. The nanowires display excellent stability while stored andmore » handled under ambient conditions over the course of weeks. Upon optical excitation, Fabry-Pérot lasing occurs in CsPbBr 3 nanowires with an onset of 5 μJ cm -2 with the nanowire cavity displaying a maximum quality factor of 1,009 ± 5. Lasing under constant, pulsed excitation can be maintained for over 1 h, the equivalent of 10 9 excitation cycles, and lasing persists upon exposure to ambient atmosphere. Wavelength tunability in the green and blue regions of the spectrum in conjunction with excellent stability makes these nanowire lasers attractive for device fabrication.« less

Polarization characteristics of Whispering-Gallery-Mode fiber lasers based on evanescent-wave-coupled gain.

PubMed

Zhang, Yuan-Xian; Pu, Xiao-Yun; Feng, Li; Han, De-Yu; Ren, Yi-Tao

2013-05-20

The polarization characteristics of Whispering-Gallery-Mode (WGM) fiber lasers based on evanescent-wave-coupled gain are investigated. For the laser gain is excited by side-pumping scheme, it is found that the polarization property of lasing emission is simply dependent on the polarized states of the pump beams. The polarization property of lasing emission depends on the propagating situation of the pump beams in an optical fiber if the laser gain is excited by evanescent-wave pumping scheme, that is, if the pump beams within the fiber are meridional beams, the lasing emission is a transverse electric (TE) wave that forms a special radial polarization emission. However, if the pump beams within the fiber are skew beams, both transverse magnetic (TM) and TE waves exist simultaneously in lasing emission that forms a special axially and radially mixed polarization emission. Pumped by skew beams, the wave-number differences between TE and TM waves are also investigated quantitatively, the results demonstrate that the wave-number difference decreases with the increase of the fiber diameter and the refractive index (RI) of the cladding solution. The observed polarization characteristics have been well explained based on lasing radiation mechanism of WGM fiber laser of gain coupled by evanescent wave.

SPECIAL ISSUE DEVOTED TO THE 25th ANNIVERSARY OF THE A.M. PROKHOROV GENERAL PHYSICS INSTITUTE: High-speed ablation of ultradeep channels by a phase-conjugate dynamically controlled passively Q-switched Nd:YAG laser

NASA Astrophysics Data System (ADS)

Basiev, T. T.; Garnov, S. V.; Klimentov, S. M.; Pivovarov, P. A.; Gavrilov, A. V.; Smetanin, S. N.; Solokhin, S. A.; Fedin, A. V.

2007-10-01

Parameters of high-speed ablation of ultradeep channels by controlled pulse trains from a single-mode phase-conjugate dynamic cavity Nd:YAG laser emitting 20-200-ns, 70-250-mJ pulses at a pulse repetition rate in a train of 40-250 kHz are studied. The optimal parameters of ablation are found, for which a long-lived region of a hot rarefied gas was maintained in the ultradeep channel, which suppressed the shielding action of the surface plasma. The control of the lasing process during ablation optimises not only the heating and plasma formation, but also the removal of the processed material in the pause between laser pulses. Adaptive regulation of lasing parameters during ablation made it possible to obtain ultradeep channels of length 8-27 mm and diameters 80-300 μm of the input and output holes in metals (aluminium, steel and Inconel 718 nickel superalloy) and ultrahard ceramics (Al2O3, AlN, SiC).

Model calculations of kinetic and fluid dynamic processes in diode pumped alkali lasers

NASA Astrophysics Data System (ADS)

Barmashenko, Boris D.; Rosenwaks, Salman; Waichman, Karol

2013-10-01

Kinetic and fluid dynamic processes in diode pumped alkali lasers (DPALs) are analyzed in detail using a semianalytical model, applicable to both static and flowing-gas devices. The model takes into account effects of temperature rise, excitation of neutral alkali atoms to high lying electronic states and their losses due to ionization and chemical reactions, resulting in a decrease of the pump absorption, slope efficiency and lasing power. Effects of natural convection in static DPALs are also taken into account. The model is applied to Cs DPALs and the results are in good agreement with measurements in a static [B.V. Zhdanov, J. Sell and R.J. Knize, Electron. Lett. 44, 582 (2008)] and 1-kW flowing-gas [A.V. Bogachev et al., Quantum Electron. 42, 95 (2012)] DPALs. It predicts the dependence of power on the flow velocity in flowing-gas DPALs and on the buffer gas composition. The maximum values of the laser power can be substantially increased by optimization of the flowing-gas DPAL parameters. In particular for the aforementioned 1 kW DPAL, 6 kW maximum power is achievable just by increasing the pump power and the temperature of the wall and the gas at the flow inlet (resulting in increase of the alkali saturated vapor density). Dependence of the lasing power on the pump power is non-monotonic: the power first increases, achieves its maximum and then decreases. The decrease of the lasing power with increasing pump power at large values of the latter is due to the rise of the aforementioned losses of the alkali atoms as a result of ionization. Work in progress applying two-dimensional computational fluid dynamics modeling of flowing-gas DPALs is also reported.

Light amplification by seeded Kerr instability

NASA Astrophysics Data System (ADS)

Vampa, G.; Hammond, T. J.; Nesrallah, M.; Naumov, A. Yu.; Corkum, P. B.; Brabec, T.

2018-02-01

Amplification of femtosecond laser pulses typically requires a lasing medium or a nonlinear crystal. In either case, the chemical properties of the lasing medium or the momentum conservation in the nonlinear crystal constrain the frequency and the bandwidth of the amplified pulses. We demonstrate high gain amplification (greater than 1000) of widely tunable (0.5 to 2.2 micrometers) and short (less than 60 femtosecond) laser pulses, up to intensities of 1 terawatt per square centimeter, by seeding the modulation instability in an Y3Al5O12 crystal pumped by femtosecond near-infrared pulses. Our method avoids constraints related to doping and phase matching and therefore can occur in a wider pool of glasses and crystals even at far-infrared frequencies and for single-cycle pulses. Such amplified pulses are ideal to study strong-field processes in solids and highly excited states in gases.

InAs based terahertz quantum cascade lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brandstetter, Martin, E-mail: martin.brandstetter@tuwien.ac.at; Kainz, Martin A.; Krall, Michael

2016-01-04

We demonstrate terahertz lasing emission from a quantum cascade structure, realized with InAs/AlAs{sub 0.16}Sb{sub 0.84} heterostructures. Due to the lower effective electron mass, InAs based active regions are expected to provide a higher optical gain compared to structures consisting of GaAs or InGaAs. The growth by molecular beam epitaxy enabled the fabrication of monolayer-thick barriers, required for the active region, which is based on a 3-well resonant phonon depletion design. Devices were processed in a double-metal waveguide geometry to ensure high mode confinement and low optical losses. Lasing emission at 3.8 THz was observed at liquid helium temperatures by applyingmore » a magnetic field perpendicular to the layered structure in order to suppress parasitic scattering channels. These results demonstrate the feasibility of InAs based active regions for terahertz quantum cascade lasers, potentially enabling higher operating temperatures.« less

Proton-Controlled Organic Microlaser Switch.

PubMed

Gao, Zhenhua; Zhang, Wei; Yan, Yongli; Yi, Jun; Dong, Haiyun; Wang, Kang; Yao, Jiannian; Zhao, Yong Sheng

2018-05-25

Microscale laser switches have been playing irreplaceable roles in the development of photonic devices with high integration levels. However, it remains a challenge to switch the lasing wavelengths across a wide range due to relatively fixed energy bands in traditional semiconductors. Here, we report a strategy to switch the lasing wavelengths among multiple states based on a proton-controlled intramolecular charge-transfer (ICT) process in organic dye-doped flexible microsphere resonant cavities. The protonic acids can effectively bind onto the ICT molecules, which thus enhance the ICT strength of the dyes and lead to a red-shifted gain behavior. On this basis, the gain region was effectively modulated by using acids with different proton-donating ability, and as a result, laser switching among multiple wavelengths was achieved. The results will provide guidance for the rational design of miniaturized lasers with performances based on the characteristic of organic optoelectronic materials.

Energy spectrum and thermal properties of a terahertz quantum-cascade laser based on the resonant-phonon depopulation scheme

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khabibullin, R. A., E-mail: khabibullin@isvch.ru; Shchavruk, N. V.; Klochkov, A. N.

The dependences of the electronic-level positions and transition oscillator strengths on an applied electric field are studied for a terahertz quantum-cascade laser (THz QCL) with the resonant-phonon depopulation scheme, based on a cascade consisting of three quantum wells. The electric-field strengths for two characteristic states of the THz QCL under study are calculated: (i) “parasitic” current flow in the structure when the lasing threshold has not yet been reached; (ii) the lasing threshold is reached. Heat-transfer processes in the THz QCL under study are simulated to determine the optimum supply and cooling conditions. The conditions of thermocompression bonding of themore » laser ridge stripe with an n{sup +}-GaAs conductive substrate based on Au–Au are selected to produce a mechanically stronger contact with a higher thermal conductivity.« less

Preventing Raman Lasing in High-Q WGM Resonators

NASA Technical Reports Server (NTRS)

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

2007-01-01

A generic design has been conceived to suppress the Raman effect in whispering- gallery-mode (WGM) optical resonators that have high values of the resonance quality factor (Q). Although it is possible to exploit the Raman effect (even striving to maximize the Raman gain to obtain Raman lasing), the present innovation is intended to satisfy a need that arises in applications in which the Raman effect inhibits the realization of the full potential of WGM resonators as frequency-selection components. Heretofore, in such applications, it has been necessary to operate high-Q WGM resonators at unattractively low power levels to prevent Raman lasing. (The Raman-lasing thresholds of WGM optical resonators are very low and are approximately proportional to Q(sup -2)). Heretofore, two ways of preventing Raman lasting at high power levels have been known, but both entail significant disadvantages: A resonator can be designed so that the optical field is spread over a relatively large mode volume to bring the power density below the threshold. For any given combination of Q and power level, there is certain mode volume wherein Raman lasing does not start. Unfortunately, a resonator that has a large mode volume also has a high spectral density, which is undesirable in a typical photonic application. A resonator can be cooled to the temperature of liquid helium, where the Raman spectrum is narrower and, therefore, the Raman gain is lower. However, liquid-helium cooling is inconvenient. The present design overcomes these disadvantages, making it possible to operate a low-spectral-density (even a single-mode) WGM resonator at a relatively high power level at room temperature, without risk of Raman lasing.

Effect of antibiotic, Lacto-lase and probiotic addition in chicken feed on protein and fat content of chicken meat

NASA Astrophysics Data System (ADS)

Azhar, Noor Amiza; Abdullah, Aminah

2015-09-01

This research was conducted to investigate the effect of chicken feed additives (antibiotic, Lacto-lase® and probiotic) on protein and fat content of chicken meat. Chicken fed with control diet (corn-soy based diet) served as a control. The treated diets were added with zinc bacitracin (antibiotic), different amount of Lacto-lase® (a mixture of probiotic and enzyme) and probiotic. Chicken were slaughtered at the age of 43-48 days. Each chicken was divided into thigh, breast, drumstick, drumette and wing. Protein content in chicken meat was determined by using macro-Kjeldahl method meanwhile Soxhlet method was used to analyse fat content. The result of the study showed that the protein content of chicken breast was significantly higher (p≤0.05) while thigh had the lowest protein content (p≤0.05). Antibiotic fed chicken was found to have the highest protein content among the treated chickens but there was no significant different with 2g/kg Lacto-lase® fed chicken (p>0.05). All thighs were significantly higher (p≤0.05) in fat content except for drumette of control chicken while breast contained the lowest fat content compared to other chicken parts studied. The control chicken meat contained significantly higher (p≤0.05) amount of fat compared to the other treated chickens. Chicken fed with 2g/kg Lacto-lase® had the lowest (p≤0.05) fat content. The result of this study indicated that the addition of Lacto-lase® as a replacement of antibiotic in chicken feed will not affect the content of protein and fat of chicken meat.

Effectiveness of silica-lasing method on the bond strength of composite resin repair to Ni-Cr alloy.

PubMed

Madani, Azam S; Astaneh, Pedram Ansari; Nakhaei, Mohammadreza; Bagheri, Hossein G; Moosavi, Horieh; Alavi, Samin; Najjaran, Niloufar Tayarani

2015-04-01

The aim of this study was to evaluate the effectiveness of silica-lasing method for improving the composite resin repair of metal ceramic restorations. Sixty Ni-Cr cylindrical specimens were fabricated. The bonding surface of all specimens was airborne-particle abraded using 50 μm aluminum oxide particles. Specimens were divided into six groups that received the following surface treatments: group 1-airborne-particle abrasion alone (AA); group 2-Nd:YAG laser irradiation (LA); group 3-silica coating (Si-CO); group 4-silica-lasing (metal surface was coated with slurry of opaque porcelain and irradiated by Nd:YAG laser) (Si-LA); group 5-silica-lasing plus etching with HF acid (Si-LA-HF); group 6-CoJet sand lased (CJ-LA). Composite resin was applied on metal surfaces. Specimens were thermocycled and tested in shear mode in a universal testing machine. The shear bond strength values were analyzed using ANOVA and Tukey's tests (α = 0.05). The mode of failure was determined, and two specimens in each group were examined by scanning electron microscopy and wavelength dispersive X-ray spectroscopy. Si-CO showed significantly higher shear bond strength in comparison to other groups (p < 0.001). The shear bond strength values of the LA group were significantly higher than those of the AA group (p < 0.05). No significant difference was found among lased groups (LA, Si-LA, Si-LA-HF, CJ-LA; p > 0.05). The failure mode was 100% adhesive for AA, Si-LA, Si-LA-HF, and CJ-LA. LA and Si-CO groups showed 37.5% and 87.5% cohesive failure, respectively. Silica coating of Ni-Cr alloy resulted in higher shear bond strength than those of other surface treatments. © 2014 by the American College of Prosthodontists.

Development of laser diode otolaryngological intracavity procedures and its clinical practice

NASA Astrophysics Data System (ADS)

Wang, Qingguo; Mao, Haitao; Bu, Hongjian; Dong, Xingfa; Li, Jikai; Li, Fangzheng; Zhang, Wenqing

1998-08-01

Because laser is diffusely reflected by the skin as well as scattered and absorbed by the subcutaneous tissue, the lasing intensity which enters into the tissue through the skin is exponentially attenuated with the increase in the depth. Therefore, when the medium-small energy laser is transmitted to the tissue depth through the skin, the lasing intensity is quite finite. However, a lot of diseases occur in the crooked and narrow tube, sinus or deep tissue, for these diseases, it is difficult to get the curative effect by normal laser radiation. As above, we have developed an otolaryngological intracavity therapeutic apparatus of laser diode. Visible GaAlAs laser diode is adopted on this apparatus, its lasing wavelength is 670 nm. The lasing beam is guided into the crooked and narrow tube, sinus or deep tissue, which passes through the optical fiber and the laser pins of different forms and sizes (such as straight, curved and sidelight etc.). Using the fiber-optic connector the laser pins can be changed conveniently. The lasing output power of laser pin can be adjusted from 0 to 20 mW. The lasing intensity may be modulated which changes the rectangular wave form 0 to 1 kHz. Five hundred patients were suffering from 35 kind of otolaryngological diseases were treated in the period of clinical test. The rate of efficiency (cure or improvement) is 89%. Nobody had the side effect or deteriorated. This apparatus has the best curative effect on the inflammation of the mucosa and shallow tissue, such as auris media dropsy, maxillary sinus inflammation, auris external inflammation, chronic laryngitis, otitis media, tinnitus, vertigo, and so on.

On pulse duration of self-terminating lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bokhan, P A

2011-02-28

The problem of the maximum pulse duration {tau}{sub max} of self-terminating lasers is considered. It is shown that the duration depends on the transition probability in the laser channel, on the decay rate of the resonant state in all other channels, and on the excitation rate of the metastable state. As a result, {tau}{sub max} is found to be significantly shorter than previously estimated. The criteria for converting the 'self-terminating' lasing to quasi-cw lasing are determined. It is shown that in the case of nonselective depopulation of the metastable state, for example in capillary lasers or in a fast flowmore » of the active medium gas, it is impossible to obtain continuous lasing. Some concrete examples are considered. It is established that in several studies of barium vapour lasers ({lambda} = 1.5 {mu}m) and nitrogen lasers ({lambda} = 337 nm), collisional lasing is obtained by increasing the relaxation rate of the metastable state in collisions with working particles (barium atoms and nitrogen molecules). (lasers)« less

Ambipolar light-emitting organic single-crystal transistors with a grating resonator

PubMed Central

Maruyama, Kenichi; Sawabe, Kosuke; Sakanoue, Tomo; Li, Jinpeng; Takahashi, Wataru; Hotta, Shu; Iwasa, Yoshihiro; Takenobu, Taishi

2015-01-01

Electrically driven organic lasers are among the best lasing devices due to their rich variety of emission colors as well as other advantages, including printability, flexibility, and stretchability. However, electrically driven lasing in organic materials has not yet been demonstrated because of serious luminescent efficiency roll-off under high current density. Recently, we found that the organic ambipolar single-crystal transistor is an excellent candidate for lasing devices because it exhibits less efficient roll-off, high current density, and high luminescent efficiency. Although a single-mode resonator combined with light-emitting transistors (LETs) is necessary for electrically driven lasing devices, the fragility of organic crystals has strictly limited the fabrication of resonators, and LETs with optical cavities have never been fabricated until now. To achieve this goal, we improved the soft ultraviolet-nanoimprint lithography method and demonstrated electroluminescence from a single-crystal LET with a grating resonator, which is a crucial milestone for future organic lasers. PMID:25959455

Profiling of Atmospheric Water Vapor with MIR and LASE

NASA Technical Reports Server (NTRS)

Wang, J. R.; Racette, P.; Triesly, M. E.; Browell, E. V.; Ismail, S.; Chang, L. A.; Hildebrand, Peter H. (Technical Monitor)

2001-01-01

This paper presents the first and the only simultaneous measurements of water vapor by MIR (Millimeter-wave Imaging Radiometer) and LASE (Lidar Atmospheric Sounding Experiment) on board the same ER-2 aircraft. Water vapor is one of the most important constituents in the Earth's atmosphere, as its spatial and temporal variations affect a wide spectrum of meteorological phenomena ranging from the formation of clouds to the development of severe storms. Its concentration, as measured in terms of relative humidity, determines the extinction coefficient of atmospheric aerosol particles and therefore visibility. These considerations point to the need for effective and frequent measurements of the atmospheric water vapor. The MIR and LASE instruments provide measurements of water vapor profiles with two markedly different techniques. LASE can give water vapor profiles with excellent vertical resolution under clear condition, while MIR can retrieve water vapor profiles with a crude vertical resolution even under a moderate cloud cover. Additionally, millimeter-wave measurements are relatively simple and provide better spatial coverage.

Mirrorless lasing from light emitters in percolating clusters

NASA Astrophysics Data System (ADS)

Burlak, Gennadiy; Rubo, Y. G.

2015-07-01

We describe the lasing effect in the three-dimensional percolation system, where the percolating cluster is filled by active media composed by light emitters excited noncoherently. We show that, due to the presence of a topologically nontrivial photonic structure, the stimulated emission is modified with respect to both conventional and random lasers. The time dynamics and spectra of the lasing output are studied numerically with finite-difference time-domain approach. The Fermat principle and Monte Carlo approach are applied to characterize the optimal optical path and interconnection between the radiating emitters. The spatial structure of the laser mode is found by a long-time FDTD simulation.

Bibliography of Soviet Laser Developments, Number 62, November-December 1982.

DTIC Science & Technology

1983-10-30

A V ill UBOV V S 26 VODOVATOV I A 76 TITOV YE A 34,96 USOVA N A 1 VOZOT B 16 TRAL’ V A 113 USTINOY N D 12,59 VOLCHENOK V 1 17 TODUA...of single pulse lasing. ZhPS, v . 37, no. 5, 1982, 741-748. 3. Zaskal’ko, O.P., and l.G. Rudoy (1). Giant pulse lasing without a resonator. ZhETF P, v ...2534. b. Er 3+ 8. Kaminskiy, A.A. (13).- Staged lasing from Er3 ions in YAlO 3crytal a4 4 1 IV 4 4a 3/2--:--3/2 ’~ A +111/2-1-

Study of nonlinear liquid effects into ytterbium-doped fiber laser for multi-wavelength generation

NASA Astrophysics Data System (ADS)

Lozano-Hernandez, T.; Jauregui-Vazquez, D.; Estudillo-Ayala, J.; Herrera-Piad, L. A.; Rojas-Laguna, R.; Hernandez-Garcia, J. M.; Sierra-Hernandez, J. M.

2018-02-01

We present an experimental study of liquid refractive index effects into Ytterbium ring fiber laser cavity configuration. The laser is operated using a bi-tapered optical fiber immersed in water-alcohol concentrations. When the tapered fiber is dipped into a distilled water, a single lasing line with a peak power centered at 1025 nm is achieved. Afterward, by changing the polarization state into the cavity the lasing line can be switched. Moreover, by modifying the refractive index liquid surrounding media the lasing lines can be controlled and special liquid provide nonlinear response. The laser offers compactness, low effective cost and good stability.

PicoGreen dye as an active medium for plastic lasers

NASA Astrophysics Data System (ADS)

Pradeep, C.; Vallabhan, C. P. G.; Radhakrishnan, P.; Nampoori, V. P. N.

2015-08-01

Deoxyribonucleic acid lipid complex thin films are used as a host material for laser dyes. We tested PicoGreen dye, which is commonly used for the quantification of single and double stranded DNA, for its applicability as lasing medium. PicoGreen dye exhibits enhanced fluorescence on intercalation with DNA. This enormous fluorescence emission is amplified in a planar microcavity to achieve yellow lasing. Here the role of DNA is not only a host medium, but also as a fluorescence dequencher. With the obtained results we have ample reasons to propose PicoGreen dye as a lasing medium, which can lead to the development of DNA based bio-lasers.

A possible upgrade of FLASH for harmonic lasing down to 1.3 nm

NASA Astrophysics Data System (ADS)

Schneidmiller, E. A.; Yurkov, M. V.

2013-07-01

We propose the 3rd harmonic lasing in a new FLASH undulator as a way to produce intense, narrow-band, and stable SASE radiation down to 1.3 nm with the present accelerator energy of 1.25 GeV. To provide optimal conditions for harmonic lasing, we suggest to suppress the fundamental with the help of a special set of phase shifters. We rely on the standard technology of gap-tunable planar hybrid undulators, and choose the period of 2.3 cm and the minimum gap of 0.9 cm; total length of the undulator system is 34.5 m. With the help of numerical simulations we demonstrate that the 3rd harmonic lasing at 1.3 nm provides peak power at a gigawatt level and the narrow intrinsic bandwidth, 0.1% (FWHM). Pulse duration can be controlled in the range of a few tens of femtoseconds, and the peak brilliance reaches the value of 1031 photons/(s mrad2 mm2 0.1% BW). With the given undulator design, a standard option of lasing at the fundamental wavelength to saturation is possible through the entire water window and at longer wavelengths. In this paper we briefly consider additional options such as polarization control, bandwidth reduction, self-seeding, X-ray pulse compression, and two-color operation. We also discuss possible technical issues and backup solutions.

Temperature changes across porcelain during multiple exposure CO2 lasing

NASA Astrophysics Data System (ADS)

Barron, Joseph R.; Zakariasen, Kenneth L.; Peacocke, Larry

1990-06-01

Research indicates that laser energy may provide a useful method for glazing and fusing porcelain for intraoral prosthetic purposes. However, it is not known whether such lasing will result in the production of heat levels that may be damaging to adjacent vital tissues such as the dental pulp and periodontal tissues. This research is designed to measure the magnitude of temperature rise across porcelain observed during multiple exposure C02 lasing. Fifteen porcelain examples of 1000 jim (5), 1500 pm (5) and 2000 tm (5) x each received five C02 laser exposures on the same exposure site at 1.0 sec. intervals at 8.0 watts (0.2 sec. per exposure with a 1 mm focal spot). A YSI 144201 thermilinear precision thermistor was placed on the porcelain surface opposite each laser exposure site. Temperature rise above ambient was recorded by an HP3421A data acquisition unit and HP9816 technical microcomputer. Recording continued for sufficient time to allow temperatures to return to ambient. The mean temperature elevations ranged from a low of 2.97 0C (2000 pm) to a high of 7.77 °C (1000 μm). ANOVA and Duncan's Multiple Range Test indicated significant differences in temperature rise by porcelain thickness. It would appear from the results of this research that temperature elevations adjacent to lased porcelain may be sufficiently controllable that safe intraoral porcelain lasing will be possible.

Development of Room Temperature Excitonic Lasing From ZnO and MgZnO Thin Film Based Metal-Semiconductor-Metal Devices

NASA Astrophysics Data System (ADS)

Suja, Mohammad Zahir Uddin

Room temperature excitonic lasing is demonstrated and developed by utilizing metal-semiconductor-metal devices based on ZnO and MgZnO materials. At first, Cu-doped p-type ZnO films are grown on c-sapphire substrates by plasma-assisted molecular beam epitaxy. Photoluminescence (PL) experiments reveal a shallow acceptor state at 0.15 eV above the valence band edge. Hall effect results indicate that a growth condition window is found for the formation of p-type ZnO thin films and the best conductivity is achieved with a high hole concentration of 1.54x1018 cm-3, a low resistivity of 0.6 O cm and a moderate mobility of 6.65 cm2 V -1 s-1 at room temperature. Metal oxide semiconductor (MOS) capacitor devices have been fabricated on the Cu-doped ZnO films and the characteristics of capacitance-voltage measurements demonstrate that the Cu-doped ZnO thin films under proper growth conditions are p-type. Seebeck measurements on these Cu-doped ZnO samples lead to positive Seebeck coefficients and further confirm the p-type conductivity. Other measurements such as XRD, XPS, Raman and absorption are also performed to elucidate the structural and optical characteristics of the Cu-doped p-type ZnO films. The p-type conductivity is explained to originate from Cu substitution of Zn with a valency of +1 state. However, all p-type samples are converted to n-type over time, which is mostly due to the carrier compensation from extrinsic defects of ZnO. To overcome the stability issue of p-type ZnO film, alternate devices other than p-n junction has been developed. Electrically driven plasmon-exciton coupled random lasing is demonstrated by incorporating Ag nanoparticles on Cu-doped ZnO metal-semiconductor-metal (MSM) devices. Both photoluminescence and electroluminescence studies show that emission efficiencies have been enhanced significantly due to coupling between ZnO excitons and Ag surface plasmons. With the incorporation of Ag nanoparticles on ZnO MSM structures, internal quantum efficiency up to 6 times is demonstrated. Threshold current for lasing is decreased by as much as 30% while the output power is increased up to 350% at an injection current of 40 mA. A numerical simulation study reveals that hole carriers are generated in the ZnO MSM devices from impact ionization processes for subsequent plasmon-exciton coupled lasing. Our results suggest that plasmon-enhanced ZnO MSM random lasers can become a competitive candidate of efficient ultraviolet light sources. Semiconductor lasers in the deep ultraviolet (UV) range have numerous potential applications ranging from water purification and medical diagnosis to high-density data storage and flexible displays. Nevertheless, very little success was achieved in the realization of electrically driven deep UV semiconductor lasers to date. In this thesis, we report the fabrication and characterization of deep UV MgZnO semiconductor lasers. These lasers are operated with continuous current mode at room temperature and the shortest wavelength reaches 284 nm. The wide bandgap MgZnO thin films with various Mg mole fractions were grown on c-sapphire substrate using radio-frequency plasma assisted molecular beam epitaxy. Metal-semiconductor-metal (MSM) random laser devices were fabricated using lithography and metallization processes. Besides the demonstration of scalable emission wavelength, very low threshold current densities of 29 33 A/cm2 are achieved. Numerical modeling reveals that impact ionization process is responsible for the generation of hole carriers in the MgZnO MSM devices. The interaction of electrons and holes leads to radiative excitonic recombination and subsequent coherent random lasing.

Optically pumped lasing in a rolled-up dot-in-a-well (DWELL) microtube via the support of Au pad

NASA Astrophysics Data System (ADS)

Chai, Zhaoer; Wang, Qi; Cao, Jiawei; Mao, Guoming; Liu, Hao; Ren, Xiaomin; Maleev, Nikolai A.; Vasil'ev, Alexey P.; Zhukov, Alexey E.; Ustinov, Victor M.

2018-02-01

We report the observation of optically pumped continuous wave lasing in a self-rolled-up InGaAs/GaAs quantum dot microtube at room temperature. Single layer of InAs quantum dots ( 2.6 ML coverage) in a GaAs well sandwiched by two AlGaAs barriers are incorporated into the tube wall as the gain media. As-fabricated microtube is supported by a 300-nm-thick Au pad, aiming to separate the tube from GaAs substrate and thus to decrease the substrate loss, which finally enables lasing with ultralow threshold power ( 4 µW) from an microtube ring resonator.

Laser action benzimidazoles in various aggregate states

NASA Astrophysics Data System (ADS)

Gruzinskii, V. V.; Degtiarenko, K. M.; Shalaev, V. K.; Kopylova, T. N.; Verkhovskii, V. S.; Tarasenko, V. F.; Melchenko, S. V.

1983-04-01

Lasing has been obtained in solutions of benzimidazole (Bi) derivatives: 2-phenyl-Bi (with the band maximum lambda-r-max = 341-347 nm), 2-n-tolyl-Bi (344 nm), and 2-(4'-biphenilyl) Bi (366-374 nm). It is found that compounds of this class provide a basis for laser radiation covering a wide region of the spectrum. Lasing has been obtained on the vapors of 2-(4'-biphenilyl) Bi (361.2 nm) and 2-(n-tolyl) Bi (336.5 nm) with a pentane stabilizer of the excited states. High volatility, photostability, and lasing in wide ranges of concentration determine the efficiency of using this new class of compounds (chain arylbenzimidazoles) in lasers using the vapors of complex molecules.

Fresh Slice Self-Seeding and Fresh Slice Harmonic Lasing at LCLS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amann, J.W.

We present results from the successful demonstration of fresh slice self-seeding at the Linac Coherent Light Source (LCLS).* The performance is compared with SASE and regular self-seeding at photon energy of 5.5 keV, resulting in a relative average brightness increase of a factor of 12 and a factor of 2 respectively. Following this proof-of-principle we discuss the forthcoming plans to use the same technique** for fresh slice harmonic lasing in an upcoming experiment. The demonstration of fresh slice harmonic lasing provides an attractive solution for future XFELs aiming to achieve high efficiency, high brightness X-ray pulses at high photon energiesmore » (>12 keV).***« less

Microoptoelectromechanical system (MOEMS) based laser

DOEpatents

Hutchinson, Donald P.

2003-11-04

A method for forming a folded laser and associated laser device includes providing a waveguide substrate, micromachining the waveguide substrate to form a folded waveguide structure including a plurality of intersecting folded waveguide paths, forming a single fold mirror having a plurality of facets which bound all ends of said waveguide paths except those reserved for resonator mirrors, and disposing a pair of resonator mirrors on opposite sides of the waveguide to form a lasing cavity. A lasing material is provided in the lasing cavity. The laser can be sealed by disposing a top on the waveguide substrate. The laser can include a re-entrant cavity, where the waveguide substrate is disposed therein, the re-entrant cavity including the single fold mirror.

Status of HiLASE project: High average power pulsed DPSSL systems for research and industry

NASA Astrophysics Data System (ADS)

Mocek, T.; Divoky, M.; Smrz, M.; Sawicka, M.; Chyla, M.; Sikocinski, P.; Vohnikova, H.; Severova, P.; Lucianetti, A.; Novak, J.; Rus, B.

2013-11-01

We introduce the Czech national R&D project HiLASE which focuses on strategic development of advanced high-repetition rate, diode pumped solid state laser (DPSSL) systems that may find use in research, high-tech industry and in the future European large-scale facilities such as HiPER and ELI. Within HiLASE we explore two major concepts: thin-disk and cryogenically cooled multislab amplifiers capable of delivering average output powers above 1 kW level in picosecond-to-nanosecond pulsed regime. In particular, we have started a programme of technology development to demonstrate the scalability of multislab concept up to the kJ level at repetition rate of 1-10 Hz.

Optical displacement sensor

DOEpatents

Carr, Dustin W [Albuquerque, NM

2008-04-08

An optical displacement sensor is disclosed which uses a vertical-cavity surface-emitting laser (VCSEL) coupled to an optical cavity formed by a moveable membrane and an output mirror of the VCSEL. This arrangement renders the lasing characteristics of the VCSEL sensitive to any movement of the membrane produced by sound, vibrations, pressure changes, acceleration, etc. Some embodiments of the optical displacement sensor can further include a light-reflective diffractive lens located on the membrane or adjacent to the VCSEL to control the amount of lasing light coupled back into the VCSEL. A photodetector detects a portion of the lasing light from the VCSEL to provide an electrical output signal for the optical displacement sensor which varies with the movement of the membrane.

New possibilities of neodymium-doped vanadate crystals as active media for diode-pumped lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vlasov, V I; Garnov, S V; Zavartsev, Yu D

The spectral and lasing parameters of Nd:GdVO{sub 4}, Nd:YVO{sub 4}, and Nd:Gd{sub 0.7}Y{sub 0.3}VO{sub 4} vanadate crystals cut along the c axis are studied. Lasing is obtained for the first time in a nonselective resonator at the {sup 4}F{sub 3/2}-{sup 4}I{sub 11/2} transition at 1065.5 nm in a Nd:GdVO{sub 4} crystal. Tuning is realised in the range from 1062.3 to 1066.1 nm and two-frequency lasing is obtained. (special issue devoted to the 25th anniversary of the a.m. prokhorov general physics institute)

Holmium-doped fluorotellurite microstructured fibers for 2.1 μm lasing.

PubMed

Yao, Chuanfei; He, Chunfeng; Jia, Zhixu; Wang, Shunbin; Qin, Guanshi; Ohishi, Yasutake; Qin, Weiping

2015-10-15

Holmium (Ho3+)-doped fluorotellurite microstructured fibers based on TeO2-BaF2-Y2O3 glasses are fabricated by using a rod-in-tube method. By using a 1.992 μm fiber laser as the pump source, lasing at 2.077 μm is obtained from a 27 cm long Ho3+-doped fluorotellurite microstructured fiber. The maximum unsaturated power is about 161 mW and the corresponding slope efficiency is up to 67.4%. The influence of fiber length on lasing at 2.1 μm is also investigated. Our results show that Ho3+-doped fluorotellurite microstructured fibers are promising gain media for 2.1 μm laser applications.

Effects of spatial nonuniformity on laser dynamics.

PubMed

Deych, L I

2005-07-22

Semiclassical equations of lasing dynamics are rederived for a lasing medium in a cavity with a spatially nonuniform dielectric constant. The nonuniformity causes a radiative coupling between modes of the empty cavity, which results in a renormalization of self- and cross-saturation coefficients. Possible manifestations of these effects in random lasers are discussed.

Nuclear pumped laser II

NASA Technical Reports Server (NTRS)

Deyoung, R. J.; Lee, J. H.; Pinkston, W. T.

1977-01-01

The first direct nuclear pumped laser using the He-2-(n,p) H-3 reaction is reported. Lasing took place on the 1.79 microns Ar I transition in a mixture of He-3-Ar at approximately 600 Torr total pressure. It was found that the electrically pulsed afterglow He-Ar laser had the same concentration profile as the nuclear pumped laser. As a result, nuclear lasing was also achieved in He-3-Xe (2.027 micron) and He-3-Kr (2.52 micron). Scaling of laser output with both thermal flux and total pressure as well as minority concentration has been completed. A peak output (He-3-Ar) of 3.7 watts has been achieved at a total pressure of 4 atm. Direct nuclear pumping of He-3-Ne has also been achieved. Nuclear pumping of a He-3-NF3 mixture was attempted, lasing in FI at approximately 7000 A, without success, although the potential lasing transitions appeared in spontaneous emission. Both NF3 and 238UF6 appear to quench spontaneous emission when they constitute more than 1% of the gas mixture.

Surface plasmon polariton laser based on a metallic trench Fabry-Perot resonator

PubMed Central

Zhu, Wenqi; Xu, Ting; Wang, Haozhu; Zhang, Cheng; Deotare, Parag B.; Agrawal, Amit; Lezec, Henri J.

2017-01-01

Recent years have witnessed a growing interest in the development of small-footprint lasers for potential applications in small-volume sensing and on-chip optical communications. Surface plasmons—electromagnetic modes evanescently confined to metal-dielectric interfaces—offer an effective route to achieving lasing at nanometer-scale dimensions when resonantly amplified in contact with a gain medium. We achieve narrow-linewidth visible-frequency lasing at room temperature by leveraging surface plasmons propagating in an open Fabry-Perot cavity formed by a flat metal surface coated with a subwavelength-thick layer of optically pumped gain medium and orthogonally bound by a pair of flat metal sidewalls. We show how the lasing threshold and linewidth can be lowered by incorporating a low-profile tapered grating on the cavity floor to couple the excitation beam into a pump surface plasmon polariton providing a strong modal overlap with the gain medium. Low-perturbation transmission-configuration sampling of the lasing plasmon mode is achieved via an evanescently coupled recessed nanoslit, opening the way to high–figure of merit refractive index sensing of analytes interacting with the open metallic trench. PMID:28989962

Effect of the pump rate and loss perturbations on the lasing dynamics of a Fabry-Perot laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, N; Ledenev, V I

2010-11-13

Transition from generation of the fundamental mode to generation of the fundamental and first modes is studied numerically under the action of nonstationary asymmetric perturbations of pump rate and loss distributions in the active medium layer. It is shown that emergence of perturbations directly leads to excitation of the first mode with significant amplitude. The regime of two-mode lasing in the presence of perturbations is shown to appear at a pump rate that is smaller than the threshold one for two-mode lasing in the absence of perturbations. It is found that the first-mode amplitude has a maximum at a frequencymore » of intermode beatings of an unfilled Fabry-Perot resonator. It is also determined that emergence of nonstationary asymmetric perturbations leads to an increase in the average intensity of the fundamental mode. Various transition regimes to two-mode lasing are compared in different types and periods of perturbations. The operability of the scheme controlling the mode composition of laser radiation is considered. (lasers)« less

Organic Solid-State Tri-Wavelength Lasing from Holographic Polymer-Dispersed Liquid Crystal and a Distributed Feedback Laser with a Doped Laser Dye and a Semiconducting Polymer Film.

PubMed

Liu, Minghuan; Liu, Yonggang; Peng, Zenghui; Wang, Shaoxin; Wang, Qidong; Mu, Quanquan; Cao, Zhaoliang; Xuan, Li

2017-05-07

Organic solid-state tri-wavelength lasing was demonstrated from dye-doped holographic polymer-dispersed liquid crystal (HPDLC) distributed feedback (DFB) laser with semiconducting polymer poly[-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene-vinylene] (MEH-PPV) and laser dye [4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran] (DCM) by a one-step holography technique, which centered at 605.5 nm, 611.9 nm, and 671.1 nm. The temperature-dependence tuning range for the tri-wavelength dye-doped HPDLC DFB laser was as high as 8 nm. The lasing emission from the 9th order HPDLC DFB laser with MEH-PPV as active medium was also investigated, which showed excellent s-polarization characterization. The diffraction order is 9th and 8th for the dual-wavelength lasing with DCM as the active medium. The results of this work provide a method for constructing the compact and cost-effective all solid-state smart laser systems, which may find application in scientific and applied research where multi-wavelength radiation is required.

Nonpolar InGaN/GaN Core-Shell Single Nanowire Lasers.

PubMed

Li, Changyi; Wright, Jeremy B; Liu, Sheng; Lu, Ping; Figiel, Jeffrey J; Leung, Benjamin; Chow, Weng W; Brener, Igal; Koleske, Daniel D; Luk, Ting-Shan; Feezell, Daniel F; Brueck, S R J; Wang, George T

2017-02-08

We report lasing from nonpolar p-i-n InGaN/GaN multi-quantum well core-shell single-nanowire lasers by optical pumping at room temperature. The nanowire lasers were fabricated using a hybrid approach consisting of a top-down two-step etch process followed by a bottom-up regrowth process, enabling precise geometrical control and high material gain and optical confinement. The modal gain spectra and the gain curves of the core-shell nanowire lasers were measured using micro-photoluminescence and analyzed using the Hakki-Paoli method. Significantly lower lasing thresholds due to high optical gain were measured compared to previously reported semipolar InGaN/GaN core-shell nanowires, despite significantly shorter cavity lengths and reduced active region volume. Mode simulations show that due to the core-shell architecture, annular-shaped modes have higher optical confinement than solid transverse modes. The results show the viability of this p-i-n nonpolar core-shell nanowire architecture, previously investigated for next-generation light-emitting diodes, as low-threshold, coherent UV-visible nanoscale light emitters, and open a route toward monolithic, integrable, electrically injected single-nanowire lasers operating at room temperature.

Nonpolar InGaN/GaN core–shell single nanowire lasers

DOE PAGES

Li, Changyi; Wright, Jeremy Benjamin; Liu, Sheng; ...

2017-01-24

We report lasing from nonpolar p-i-n InGaN/GaN multi-quantum well core–shell single-nanowire lasers by optical pumping at room temperature. The nanowire lasers were fabricated using a hybrid approach consisting of a top-down two-step etch process followed by a bottom-up regrowth process, enabling precise geometrical control and high material gain and optical confinement. The modal gain spectra and the gain curves of the core–shell nanowire lasers were measured using micro-photoluminescence and analyzed using the Hakki-Paoli method. Significantly lower lasing thresholds due to high optical gain were measured compared to previously reported semipolar InGaN/GaN core–shell nanowires, despite significantly shorter cavity lengths and reducedmore » active region volume. Mode simulations show that due to the core–shell architecture, annular-shaped modes have higher optical confinement than solid transverse modes. Furthermore, the results show the viability of this p-i-n nonpolar core–shell nanowire architecture, previously investigated for next-generation light-emitting diodes, as low-threshold, coherent UV–visible nanoscale light emitters, and open a route toward monolithic, integrable, electrically injected single-nanowire lasers operating at room temperature.« less

CW YVO4:Er Laser with Resonant Pumping

NASA Astrophysics Data System (ADS)

Gorbachenya, K. N.; Kisel, V. E.; Yasukevich, A. S.; Matrosov, V. N.; Tolstik, N. A.; Kuleshov, N. V.

2015-05-01

The lasing characteristics of a YVO4:Er laser with resonant pumping in the 1.5-1.6 μm range are studied. Lasing is obtained at λ = 1603 nm with a differential efficiency of up to 61%. YVO4:Er crystals are found to offer promise for use in efficient resonantly (in-band) pumped lasers.

Lasing characteristics of InAs quantum dot laers on InP substrate

NASA Technical Reports Server (NTRS)

Yang, Y.; Qiu, D.; Uhl, R.; Chacon, R.

2003-01-01

Single-stack InAs self-assembled quantum dots (QD) lasers based on InP substrate have been grown by metalorganic vapor phase epitaxy. The narrow ridge waveguide lasers lased up to 260 K in continuous wave operation, and near room temperature in pulsed mode, with wavelengths between 1.59 to 1.74 mu m.

Effect of modulation p-doping level on multi-state lasing in InAs/InGaAs quantum dot lasers having different external loss

NASA Astrophysics Data System (ADS)

Korenev, V. V.; Savelyev, A. V.; Maximov, M. V.; Zubov, F. I.; Shernyakov, Yu. M.; Kulagina, M. M.; Zhukov, A. E.

2017-09-01

The influence of the modulation p-doping level on multi-state lasing in InAs/InGaAs quantum dot (QD) lasers is studied experimentally for devices having various external losses. It is shown that in the case of short cavities (high external loss), there is an increase in the lasing power component corresponding to the ground-state optical transitions of QDs as the p-doping level grows. However, in the case of long cavities (small external loss), higher dopant concentrations may have an opposite effect on the output power. Based on these observations, an optimal design of laser geometry and an optimal doping level are discussed.

Analytical model of ground-state lasing phenomenon in broadband semiconductor quantum dot lasers

NASA Astrophysics Data System (ADS)

Korenev, Vladimir V.; Savelyev, Artem V.; Zhukov, Alexey E.; Omelchenko, Alexander V.; Maximov, Mikhail V.

2013-05-01

We introduce an analytical approach to the description of broadband lasing spectra of semiconductor quantum dot lasers emitting via ground-state optical transitions of quantum dots. The explicit analytical expressions describing the shape and the width of lasing spectra as well as their temperature and injection current dependences are obtained in the case of low homogeneous broadening. It is shown that in this case these dependences are determined by only two dimensionless parameters, which are the dispersion of the distribution of QDs over the energy normalized to the temperature and loss-to-maximum gain ratio. The possibility of optimization of laser's active region size and structure by using the intentionally introduced disorder is also carefully considered.

Brillouin lasing in coupled silica toroid microcavities

NASA Astrophysics Data System (ADS)

Honda, Yoshihiro; Yoshiki, Wataru; Tetsumoto, Tomohiro; Fujii, Shun; Furusawa, Kentaro; Sekine, Norihiko; Tanabe, Takasumi

2018-05-01

We demonstrate stimulated Brillouin scattering lasing in a strongly coupled microcavity system. By coupling two silica toroid microcavities, we achieve large mode splitting of 11 GHz, whose frequency separation matches the Brillouin frequency shift of silica. The stimulated Brillouin scattering light is resonantly amplified by pumping at the higher frequency side of the supermode splitting resonance. Since the mode splitting is adjusted by changing the gap distance between the two cavities, our system does not require precise control of a mm-sized cavity diameter to match the free-spectral spacing with the Brillouin frequency shift. It also allows us to use a small cavity, and hence, our system has the potential to achieve the lasing threshold at a very low power.

Low-threshold photonic-band-edge laser using iron-nail-shaped rod array

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Jae-Hyuck; No, You-Shin; Hwang, Min-Soo

2014-03-03

We report the experimental demonstration of an optically pumped rod-type photonic-crystal band-edge laser. The structure consists of a 20 × 20 square lattice array of InGaAsP iron-nail-shaped rods. A single-mode lasing action is observed with a low threshold of ∼90 μW and a peak wavelength of 1451.5 nm at room temperature. Measurements of the polarization-resolved mode images and lasing wavelengths agree well with numerical simulations, which confirm that the observed lasing mode originates from the first Γ-point transverse-electric-like band-edge mode. We believe that this low-threshold band-edge laser will be useful for the practical implementation of nanolasers.

Design of Advanced Atmospheric Water Vapor Differential Absorption Lidar (DIAL) Detection System

NASA Technical Reports Server (NTRS)

Refaat, Tamer F.; Luck, William S., Jr.; DeYoung, Russell J.

1999-01-01

The measurement of atmospheric water vapor is very important for understanding the Earth's climate and water cycle. The lidar atmospheric sensing experiment (LASE) is an instrument designed and operated by the Langley Research Center for high precision water vapor measurements. The design details of a new water vapor lidar detection system that improves the measurement sensitivity of the LASE instrument by a factor of 10 are discussed. The new system consists of an advanced, very low noise, avalanche photodiode (APD) and a state-of-the-art signal processing circuit. The new low-power system is also compact and lightweight so that it would be suitable for space flight and unpiloted atmospheric vehicles (UAV) applications. The whole system is contained on one small printed circuit board (9 x 15 sq cm). The detection system is mounted at the focal plane of a lidar receiver telescope, and the digital output is read by a personal computer with a digital data acquisition card.

Optical gain in colloidal quantum dots achieved with direct-current electrical pumping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, Jaehoon; Park, Young-Shin; Klimov, Victor Ivanovich

Chemically synthesized semiconductor quantum dots (QDs) can potentially enable solution-processable laser diodes with a wide range of operational wavelengths, yet demonstrations of lasing from the QDs are still at the laboratory stage. An important challenge—realization of lasing with electrical injection—remains unresolved, largely due to fast nonradiative Auger recombination of multicarrier states that represent gain-active species in the QDs. Here in this paper, we present population inversion and optical gain in colloidal nanocrystals realized with direct-current electrical pumping. Using continuously graded QDs, we achieve a considerable suppression of Auger decay such that it can be outpaced by electrical injection. Further, wemore » apply a special current-focusing device architecture, which allows us to produce high current densities (j) up to ~18 A cm -2 without damaging either the QDs or the injection layers. The quantitative analysis of electroluminescence and current-modulated transmission spectra indicates that with j = 3-4 A cm -2 we achieve the population inversion of the band-edge states.« less

Optical gain in colloidal quantum dots achieved with direct-current electrical pumping

NASA Astrophysics Data System (ADS)

Lim, Jaehoon; Park, Young-Shin; Klimov, Victor I.

2018-01-01

Chemically synthesized semiconductor quantum dots (QDs) can potentially enable solution-processable laser diodes with a wide range of operational wavelengths, yet demonstrations of lasing from the QDs are still at the laboratory stage. An important challenge--realization of lasing with electrical injection--remains unresolved, largely due to fast nonradiative Auger recombination of multicarrier states that represent gain-active species in the QDs. Here we present population inversion and optical gain in colloidal nanocrystals realized with direct-current electrical pumping. Using continuously graded QDs, we achieve a considerable suppression of Auger decay such that it can be outpaced by electrical injection. Further, we apply a special current-focusing device architecture, which allows us to produce high current densities (j) up to ~18 A cm-2 without damaging either the QDs or the injection layers. The quantitative analysis of electroluminescence and current-modulated transmission spectra indicates that with j = 3-4 A cm-2 we achieve the population inversion of the band-edge states.

Optical gain in colloidal quantum dots achieved with direct-current electrical pumping

DOE PAGES

Lim, Jaehoon; Park, Young-Shin; Klimov, Victor Ivanovich

2017-11-20

Chemically synthesized semiconductor quantum dots (QDs) can potentially enable solution-processable laser diodes with a wide range of operational wavelengths, yet demonstrations of lasing from the QDs are still at the laboratory stage. An important challenge—realization of lasing with electrical injection—remains unresolved, largely due to fast nonradiative Auger recombination of multicarrier states that represent gain-active species in the QDs. Here in this paper, we present population inversion and optical gain in colloidal nanocrystals realized with direct-current electrical pumping. Using continuously graded QDs, we achieve a considerable suppression of Auger decay such that it can be outpaced by electrical injection. Further, wemore » apply a special current-focusing device architecture, which allows us to produce high current densities (j) up to ~18 A cm -2 without damaging either the QDs or the injection layers. The quantitative analysis of electroluminescence and current-modulated transmission spectra indicates that with j = 3-4 A cm -2 we achieve the population inversion of the band-edge states.« less

Towards zero-threshold optical gain using charged semiconductor quantum dots

DOE PAGES

Wu, Kaifeng; Park, Young -Shin; Lim, Jaehoon; ...

2017-10-16

Colloidal semiconductor quantum dots are attractive materials for the realization of solution-processable lasers. However, their applications as optical-gain media are complicated by a non-unity degeneracy of band-edge states, because of which multiexcitons are required to achieve the lasing regime. This increases the lasing thresholds and leads to very short optical gain lifetimes limited by nonradiative Auger recombination. Here, we show that these problems can be at least partially resolved by employing not neutral but negatively charged quantum dots. By applying photodoping to specially engineered quantum dots with impeded Auger decay, we demonstrate a considerable reduction of the optical gain thresholdmore » due to suppression of ground-state absorption by pre-existing carriers. Moreover, by injecting approximately one electron per dot on average, we achieve a more than twofold reduction in the amplified spontaneous emission threshold, bringing it to the sub-single-exciton level. Furthermore, these measurements indicate the feasibility of ‘zero-threshold’ gain achievable by completely blocking the band-edge state with two electrons.« less

Laser performance of Coumarin 540A dye molecules in polymeric host media with different viscosities: From liquid solution to solid polymer matrix

DOE Office of Scientific and Technical Information (OSTI.GOV)

Costela, A.; Garcia-Moreno, I.; Barroso, J.

1998-01-01

Photophysical parameters and lasing properties of Coumarin 540A dye molecules are studied in solutions of increasing viscosity, from liquid solutions in 1,4-dioxane to solid solutions in poly(methyl methacrylate). The fluorescence quantum yield and lasing efficiencies decrease as the viscosity of the solution increases, reflecting the strong influence of the rigidity of the medium on the radiative processes. The photodegradation mechanisms acting on the fluorophores are analyzed by following the dependence of laser induced fluorescence and laser output on the number of pump laser pulses. The fluorescence redistribution after pattern photobleaching technique is used, and Fick{close_quote}s second law is applied tomore » study the diffusion of dye molecules in the highly viscous polymer solutions. The diffusion coefficients of the dye molecules as a function of the increased viscosity of the medium are determined. {copyright} {ital 1998 American Institute of Physics.}« less

Coupling effects in the modal emission of colloidal quantum dot microdisk lasers.

NASA Astrophysics Data System (ADS)

Lafalce, Evan; Zheng, Qingji; Lin, Chunhao; Smith, Marcus; Malak, Sidney; Jung, Jaehan; Yoon, Young; Lin, Zhiqun; Tsukruk, Vladimir; Vardeny, Z. Valy

Solution-processed semiconductors such as colloidal quantum dots (CQD) are particularly suited materials for monolithic fabrication of laser microstructures because of their ease of fabrication and compatibility with conventional lithographic techniques. We use the functionality of core/alloyed-shell CQDs to fabricate microdisk lasers of variable size and study the resulting whispering-gallery mode laser emission. In particular we study the effects of near-field coupling on resonant modes of pairs of these lasers with sub-micrometer spacing. We demonstrate the occurrence of lasing modes that originate from the interaction between two such microdisks by means of varying the spatial distribution and magnitude of the gain and loss in the coupled-pair. The transition from emission of modes localized on a single disk to those of the interacting pair is accompanied by coalescence of eigen-frequencies and pump-induced turn-off of lasing, highlighting the role of parity-time symmetry and exceptional point physics. This work was funded by AFOSR through MURI Grant RA 9550-14-1-0037.

Towards zero-threshold optical gain using charged semiconductor quantum dots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Kaifeng; Park, Young -Shin; Lim, Jaehoon

Colloidal semiconductor quantum dots are attractive materials for the realization of solution-processable lasers. However, their applications as optical-gain media are complicated by a non-unity degeneracy of band-edge states, because of which multiexcitons are required to achieve the lasing regime. This increases the lasing thresholds and leads to very short optical gain lifetimes limited by nonradiative Auger recombination. Here, we show that these problems can be at least partially resolved by employing not neutral but negatively charged quantum dots. By applying photodoping to specially engineered quantum dots with impeded Auger decay, we demonstrate a considerable reduction of the optical gain thresholdmore » due to suppression of ground-state absorption by pre-existing carriers. Moreover, by injecting approximately one electron per dot on average, we achieve a more than twofold reduction in the amplified spontaneous emission threshold, bringing it to the sub-single-exciton level. Furthermore, these measurements indicate the feasibility of ‘zero-threshold’ gain achievable by completely blocking the band-edge state with two electrons.« less

Qualitative analysis of gain spectra of InGaAlAs/InP lasing nano-heterostructure

NASA Astrophysics Data System (ADS)

Lal, Pyare; Yadav, Rashmi; Sharma, Meha; Rahman, F.; Dalela, S.; Alvi, P. A.

2014-08-01

This paper deals with the studies of lasing characteristics along with the gain spectra of compressively strained and step SCH based In0.71Ga0.21Al0.08As/InP lasing nano-heterostructure within TE polarization mode, taking into account the variation in well width of the single quantum well of the nano-heterostructure. In addition, the compressive conduction and valence bands dispersion profiles for quantum well of the material composition In0.71Ga0.21Al0.08As at temperature 300 K and strain 1.12% have been studied using 4 × 4 Luttinger Hamiltonian. For the proposed nano-heterostructure, the quantum well width dependence of differential gain, refractive index change and relaxation oscillation frequency with current density have been studied. Moreover, the G-J characteristics of the nano-heterostructure at different well widths have also been investigated, that provided significant information about threshold current density, threshold gain and transparency current density. The results obtained in the study of nano-heterostructure suggest that the gain and relaxation oscillation frequency both are decreased with increasing quantum well width but the required lasing wavelength is found to shift towards higher values. On behalf of qualitative analysis of the structure, the well width of 6 nm is found more suitable for lasing action at the wavelength of 1.55 μm due to minimum optical attenuation and minimum dispersion within the waveguide. The results achieved are, therefore, very important in the emerging area of nano-optoelectronics.

LASE Measurements of Water Vapor, Aerosol, and Cloud Distributions in Saharan Air Layers and Tropical Disturbances

NASA Technical Reports Server (NTRS)

Ismail, Syed; Ferrare, Richard A.; Browell, Edward V.; Kooi, Susan A.; Dunion, Jason P.; Heymsfield, Gerry; Notari, Anthony; Butler, Carolyn F.; Burton, Sharon; Fenn, Marta;

Broad Wavelength Tunable Robust Lasing from Single-Crystal Nanowires of Cesium Lead Halide Perovskites (CsPbX3, X = Cl, Br, I).

PubMed

Fu, Yongping; Zhu, Haiming; Stoumpos, Constantinos C; Ding, Qi; Wang, Jue; Kanatzidis, Mercouri G; Zhu, Xiaoyang; Jin, Song

2016-08-23

Lead halide perovskite nanowires (NWs) are emerging as a class of inexpensive semiconductors with broad bandgap tunability for optoelectronics, such as tunable NW lasers. Despite exciting progress, the current organic-inorganic hybrid perovskite NW lasers suffer from limited tunable wavelength range and poor material stability. Herein, we report facile solution growth of single-crystal NWs of inorganic perovskite CsPbX3 (X = Br, Cl) and their alloys [CsPb(Br,Cl)3] and a low-temperature vapor-phase halide exchange method to convert CsPbBr3 NWs into perovskite phase CsPb(Br,I)3 alloys and metastable CsPbI3 with well-preserved perovskite crystal lattice and NW morphology. These single crystalline NWs with smooth end facets and subwavelength dimensions are ideal Fabry-Perot cavities for NW lasers. Optically pumped tunable lasing across the entire visible spectrum (420-710 nm) is demonstrated at room temperature from these NWs with low lasing thresholds and high-quality factors. Such highly efficient lasing similar to what can be achieved with organic-inorganic hybrid perovskites indicates that organic cation is not essential for light emission application from these lead halide perovskite materials. Furthermore, the CsPbBr3 NW lasers show stable lasing emission with no measurable degradation after at least 8 h or 7.2 × 10(9) laser shots under continuous illumination, which are substantially more robust than their organic-inorganic counterparts. The Cs-based perovskites offer a stable material platform for tunable NW lasers and other nanoscale optoelectronic devices.

Passive cavity surface-emitting lasers: option of temperature-insensitive lasing wavelength for uncooled dense wavelength division multiplexing systems

NASA Astrophysics Data System (ADS)

Shchukin, V. A.; Ledentsov, N. N.; Slight, T.; Meredith, W.; Gordeev, N. Y.; Nadtochy, A. M.; Payusov, A. S.; Maximov, M. V.; Blokhin, S. A.; Blokhin, A. A.; Zadiranov, Yu. M.; Maleev, N. A.; Ustinov, V. M.; Choquette, K. D.

2016-03-01

A concept of passive cavity surface-emitting laser is proposed aimed to control the temperature shift of the lasing wavelength. The device contains an all-semiconductor bottom distributed Bragg reflector (DBR), in which the active medium is placed, a dielectric resonant cavity and a dielectric top DBR, wherein at least one of the dielectric materials has a negative temperature coefficient of the refractive index, dn/dT < 0. This is shown to be the case for commonly used dielectric systems SiO2/TiO2 and SiO2/Ta2O5. Two SiO2/TiO2 resonant structures having a cavity either of SiO2 or TiO2 were deposited on a substrate, their optical power reflectance spectra were measured at various temperatures, and refractive index temperature coefficients were extracted, dn/dT = 0.0021 K-1 for SiO2 and dn/dT = -0.0092 K-1 for TiO2. Using such dielectric materials allows designing passive cavity surface-emitting lasers having on purpose either positive, or zero, or negative temperature shift of the lasing wavelength dλ/dT. A design for temperature-insensitive lasing wavelength (dλ/dT = 0) is proposed. Employing devices with temperature-insensitive lasing wavelength in wavelength division multiplexing systems may allow significant reducing of the spectral separation between transmission channels and an increase in number of channels for a defined spectral interval enabling low cost energy efficient uncooled devices.

White random lasing in mixture of ZnSe, CdS and CdSSe micropowders

NASA Astrophysics Data System (ADS)

Alyamani, A. Y.; Leanenia, M. S.; Alanazi, L. M.; Aljohani, M. M.; Aljariwi, A. A.; Rzheutski, M. V.; Lutsenko, E. V.; Yablonskii, G. P.

2016-03-01

Room temperature random lasing with white light emission in a mixture of AIIBVI semiconductor powders was achieved for the first time. The scattering gain media was formed by the mixture of closely packed active micron sized crystallites of ZnSe, CdS, CdSSe semiconductors. The micropowders were produced by grinding bulk crystals of each compound. Optical excitation was performed by 10-nanosecond pulses of tuned Ti:Al2O3-laser at 390 nm. The lasing in the mixture of semiconductor powders was achieved simultaneously at four wavelengths in blue, green, yellow and red spectral regions after exceeding the threshold excitation power density. A drastic integral intensity increase, spectrum narrowing and appearance of mode structure accompanied the laser action. ZnSe crystallites produce the laser light at about 460 nm while CdS particles - at about 520 nm. Two types of CdSSe semiconductor micropowders with different sulfur content lase at 580 nm and 660 nm. The threshold excitation power densities for all laser lines in the emission spectrum are approximately the same of about 0.9 MW/cm2. The sum of the emission spectrum of the mixture of the micropowders forms white light with high brightness. Lasing is due to an appearance of random feedback for amplified radiation in the active medium of closely packed light scattering crystallites. The presented results may find their applications for visualization systems, lighting technology, data transmission, medicine as biosensors and in identification systems. The key feature of random lasers is low cost of its production and possibility to be deposited on any type of surface.

Metal atom oxidation laser

DOEpatents

Jensen, R.J.; Rice, W.W.; Beattie, W.H.

1975-10-28

A chemical laser which operates by formation of metal or carbon atoms and reaction of such atoms with a gaseous oxidizer in an optical resonant cavity is described. The lasing species are diatomic or polyatomic in nature and are readily produced by exchange or other abstraction reactions between the metal or carbon atoms and the oxidizer. The lasing molecules may be metal or carbon monohalides or monoxides.

Diode-pumped SrMoO4:Tm3+ crystal lasing near 1500 nm

NASA Astrophysics Data System (ADS)

Doroshenko, M. E.; Sulc, J.; Jelinkova, H.; Nemec, M.; Ivleva, L. I.; Dunaeva, E. E.

2018-04-01

Diode-pumped lasing of Tm3+ ions in SrMoO4 crystal at wavelength near 1500 nm was obtained for the first time to our best knowledge. Two laser lines with orthogonal polarizations were observed at 1452 and 1492 nm. The laser pulse was self-terminated about 500 µs after the pump start.

High average power laser using a transverse flowing liquid host

DOEpatents

Ault, Earl R.; Comaskey, Brian J.; Kuklo, Thomas C.

2003-07-29

A laser includes an optical cavity. A diode laser pumping device is located within the optical cavity. An aprotic lasing liquid containing neodymium rare earth ions fills the optical cavity. A circulation system that provides a closed loop for circulating the aprotic lasing liquid into and out of the optical cavity includes a pump and a heat exchanger.

Diode-pumped laser with improved pumping system

DOEpatents

Chang, Jim J.

2004-03-09

A laser wherein pump radiation from laser diodes is delivered to a pump chamber and into the lasing medium by quasi-three-dimensional compound parabolic concentrator light channels. The light channels have reflective side walls with a curved surface and reflective end walls with a curved surface. A flow tube between the lasing medium and the light channel has a roughened surface.

Explosive laser light initiation of propellants

DOEpatents

Piltch, Martin S.

1993-01-01

A improved initiator for artillery shell using an explosively generated laser light to uniformly initiate the propellent. A small quantity of a high explosive, when detonated, creates a high pressure and temperature, causing the surrounding noble gas to fluoresce. This fluorescence is directed into a lasing material, which lases, and directs laser light into a cavity in the propellant, uniformly initiating the propellant.

Explosive laser light initiation of propellants

DOEpatents

Piltch, M.S.

1993-05-18

A improved initiator for artillery shell using an explosively generated laser light to uniformly initiate the propellent. A small quantity of a high explosive, when detonated, creates a high pressure and temperature, causing the surrounding noble gas to fluoresce. This fluorescence is directed into a lasing material, which lases, and directs laser light into a cavity in the propellant, uniformly initiating the propellant.

Dual-color single-mode lasing in axially coupled organic nanowire resonators

PubMed Central

Zhang, Chunhuan; Zou, Chang-Ling; Dong, Haiyun; Yan, Yongli; Yao, Jiannian; Zhao, Yong Sheng

2017-01-01

Miniaturized lasers with multicolor output and high spectral purity are of crucial importance for yielding more compact and more versatile photonic devices. However, multicolor lasers usually operate in multimode, which largely restricts their practical applications due to the lack of an effective mode selection mechanism that is simultaneously applicable to multiple wavebands. We propose a mutual mode selection strategy to realize dual-color single-mode lasing in axially coupled cavities constructed from two distinct organic self-assembled single-crystal nanowires. The unique mode selection mechanism in the heterogeneously coupled nanowires was elucidated experimentally and theoretically. With each individual nanowire functioning as both the laser source and the mode filter for the other nanowire, dual-color single-mode lasing was successfully achieved in the axially coupled heterogeneous nanowire resonators. Furthermore, the heterogeneously coupled resonators provided multiple nanoscale output ports for delivering coherent signals with different colors, which could greatly contribute to increasing the integration level of functional photonic devices. These results advance the fundamental understanding of the lasing modulation in coupled cavity systems and offer a promising route to building multifunctional nanoscale lasers for high-level practical photonic integrations. PMID:28785731

AquaLase versus NeoSoniX--a comparison study.

PubMed

Jiraskova, Nada; Rozsival, Pavel; Kadlecova, Jana; Nekolova, Jana; Pozlerova, Jana; Dubravska, Zlatica

2007-12-01

To compare the metrics and surgical outcome when using Infiniti AquaLase and NeoSoniX cataract removal modalities. This prospective clinical study involved 50 patients with bilateral cataracts and lens removal using AquaLase in the right eye and NeoSoniX in the left eye. Best corrected visual acuity (BCVA), endothelial cell density and pachymetry were evaluted pre- and postoperatively. Statistical analysis was performed using the Wilcoxon Signed- Rank Test. Preoperative mean pachymetry was 569 +/- 31 mu in the right eye (RE) and 560 +/- 37 mu in the left eye (LE), mean endothelial cell density 2744 +/- 418 cells/mm(2) (RE) and 2730 +/- 472 cells/mm(2) (LE). One week after operation pachymetry was 576 +/- 52 mu (RE) and 583 +/- 72 mu (LE) and endothelial cell density 2388 +/- 586 cells/mm(2) (RE) and 2463 +/- 615 cells/mm(2) (LE). One month after surgery pachymetry was 556 +/- 43 mu (RE) and 559 +/- 44 mu (LE) and endothelial cell density 2368 +/- 52 cells/mm(2) (RE) and 2495 +/- 548 cells/mm(2) (LE). BCVA improved in all eyes and was 0.8 or better on the first postoperative day. Both the NeosoniX and AquaLase minimize intraoperative damage to ocular structures.

Femtosecond lasers for laser in situ keratomileusis: a systematic review and meta-analysis

PubMed Central

Huhtala, Anne; Pietilä, Juhani; Mäkinen, Petri; Uusitalo, Hannu

2016-01-01

Purpose The aim of this study was to review and meta-analyze whether there are differences between reported femtosecond (FS) lasers for laser-assisted in situ keratomileusis (LASIK) in terms of efficacy, predictability, and safety as primary outcomes and corneal flap thickness measurements and pre- and postoperative complications as secondary outcomes. Methods A comprehensive literature search of PubMed, Science Direct, Scopus, and Cochrane CENTRAL Trials Library databases was conducted to identify the relevant prospective randomized controlled trials of FS lasers for LASIK. Thirty-one articles describing a total of 5,404 eyes were included. Results Based on efficacy, IntraLase FS 10 and 30 kHz gave the best results. Based on predictability and safety, there were no differences between various FS lasers. FEMTO LDV and IntraLase FS 60 kHz produced the most accurate flap thicknesses. IntraLase and Wavelight SF200 had the fewest intraoperative complications. IntraLase, Visumax, and Wavelight FS200 had the most seldom postoperative complications. Conclusion There were dissimilarities between different FS lasers based on efficacy and intraoperative and postoperative complications. All FS lasers were predictable and safe for making corneal flaps in LASIK. PMID:27022236

Effect of oscillator strength and intermediate resonance on the performance of resonant phonon-based terahertz quantum cascade lasers

NASA Astrophysics Data System (ADS)

Fathololoumi, S.; Dupont, E.; Wasilewski, Z. R.; Chan, C. W. I.; Razavipour, S. G.; Laframboise, S. R.; Huang, Shengxi; Hu, Q.; Ban, D.; Liu, H. C.

2013-03-01

We experimentally investigated the effect of oscillator strength (radiative transition diagonality) on the performance of resonant phonon-based terahertz quantum cascade lasers that have been optimized using a simplified density matrix formalism. Our results show that the maximum lasing temperature (Tmax) is roughly independent of laser transition diagonality within the lasing frequency range of the devices under test (3.2-3.7 THz) when cavity loss is kept low. Furthermore, the threshold current can be lowered by employing more diagonal transition designs, which can effectively suppress parasitic leakage caused by intermediate resonance between the injection and the downstream extraction levels. Nevertheless, the current carrying capacity through the designed lasing channel in more diagonal designs may sacrifice even more, leading to electrical instability and, potentially, complete inhibition of the device's lasing operation. We propose a hypothesis based on electric-field domain formation and competition/switching of different current-carrying channels to explain observed electrical instability in devices with lower oscillator strengths. The study indicates that not only should designers maximize Tmax during device optimization but also they should always consider the risk of electrical instability in device operation.

Femtosecond lasers for laser in situ keratomileusis: a systematic review and meta-analysis.

PubMed

Huhtala, Anne; Pietilä, Juhani; Mäkinen, Petri; Uusitalo, Hannu

2016-01-01

The aim of this study was to review and meta-analyze whether there are differences between reported femtosecond (FS) lasers for laser-assisted in situ keratomileusis (LASIK) in terms of efficacy, predictability, and safety as primary outcomes and corneal flap thickness measurements and pre- and postoperative complications as secondary outcomes. A comprehensive literature search of PubMed, Science Direct, Scopus, and Cochrane CENTRAL Trials Library databases was conducted to identify the relevant prospective randomized controlled trials of FS lasers for LASIK. Thirty-one articles describing a total of 5,404 eyes were included. Based on efficacy, IntraLase FS 10 and 30 kHz gave the best results. Based on predictability and safety, there were no differences between various FS lasers. FEMTO LDV and IntraLase FS 60 kHz produced the most accurate flap thicknesses. IntraLase and Wavelight SF200 had the fewest intraoperative complications. IntraLase, Visumax, and Wavelight FS200 had the most seldom postoperative complications. There were dissimilarities between different FS lasers based on efficacy and intraoperative and postoperative complications. All FS lasers were predictable and safe for making corneal flaps in LASIK.

Laser-emission imaging of nuclear biomarkers for high-contrast cancer screening and immunodiagnosis

PubMed Central

Chen, Yu-Cheng; Tan, Xiaotian; Sun, Qihan; Chen, Qiushu; Wang, Wenjie; Fan, Xudong

2017-01-01

Detection of nuclear biomarkers such as nucleic acids and nuclear proteins is critical for early-stage cancer diagnosis and prognosis. Conventional methods relying on morphological assessment of cell nuclei in histopathology slides may be subjective, whereas colorimetric immunohistochemical and fluorescence-based imaging are limited by strong light absorption, broad-emission bands and low contrast. Here, we describe the development and use of a scanning laser-emission-based microscope that maps lasing emissions from nuclear biomarkers in human tissues. 41 tissue samples from 35 patients labelled with site-specific and biomarker-specific antibody-conjugated dyes were sandwiched in a Fabry-Pérot microcavity while an excitation laser beam built a laser-emission image. We observed multiple sub-cellular lasing emissions from cancer cell nuclei, with a threshold of tens of μJ/mm2, sub-micron resolution (<700 nm), and a lasing band in the few-nanometre range. Different lasing thresholds of nuclei in cancer and normal tissues enabled the identification and multiplexed detection of nuclear proteomic biomarkers, with a high sensitivity for early-stage cancer diagnosis. Laser-emission-based cancer screening and immunodiagnosis might find use in precision medicine and facilitate research in cell biology. PMID:29204310

Multiple-wavelength vertical cavity laser arrays with wide wavelength span and high uniformity

NASA Astrophysics Data System (ADS)

Yuen, Wupen; Li, Gabriel S.; Chang-Hasnain, Connie J.

1996-12-01

Vertical-cavity surface-emitting lasers (VCSELs) are promising for numerous applications. In particular, due to their inherent single Fabry-Perot mode operation, VCSELs can be very useful for wavelength division multiplexing (WDM) systems allowing high bandwidth and high functionalities.1, 2 Multiple wavelength VCSEL arrays with wide channel spacings (>10 nm) provide an inexpensive solution to increasing the capacity of local area networks without using active wavelength controls.1 The lasing wavelength of a VCSEL is determined by the equivalent laser cavity thickness which can be varied by changing the thickness of either the l-spacer or the distributed Bragg reflector (DBR) layers. To make monolithic multiple-wavelength VCSEL arrays, the lasing wavelength, and therefore the cavity thickness, has to be varied at reasonable physical distances. For all practical applications, it is imperative for the fabrication technology to be controllable, cost-effective, and wafer-scale. Recently, we demonstrated a patterned-substrate molecular beam epitaxy (MBE) growth technique with in-situ laser reflectometry monitoring for fabricating multiple wavelength VCSEL arrays.3, 4 With this method, VCSEL arrays with very large and highly controllable lasing wavelength spans and excellent lasing characteristics have been achieved.

Theoretical studies of solar-pumped lasers

NASA Technical Reports Server (NTRS)

Harries, W. L.

1983-01-01

Metallic vapor lasers of Na2 and Li2 are examined as solar energy converters. The absorbed photons cause transitions to vibrational-rotational levels in an upper electronic state. With broad band absorption the resultant levels can have quantum numbers considerably higher than the upper lasing level. The excited molecule then relaxes to the upper lasing level which is one of the lower vibrational levels in the upper electronic state. The relaxation occurs from collisions, provided the molecule is not quenched into the ground level electronic state. Lasing occurs with a transition to a vibrational level in the lower electronic state. Rough estimates of solar power efficiencies are 1 percent for Na2 and probably a similar figure for Li2. The nondissociative lasers from a family distinct from materials which dissociate to yield an excited atom.

Tunable and mode-locked laser action of Cr4+ in codoped forsterite Cr, Sc:Mg2SiO4

NASA Astrophysics Data System (ADS)

Sanina, V. V.; Mitrokhin, V. P.; Subbotin, K. A.; Lis, D. A.; Lis, O. N.; Ivanov, A. A.; Zharikov, E. V.

2018-01-01

The laser oscillation of tetravalent chromium and scandium codoped forsterite Cr4+,Sc:Mg2SiO4 single crystal has been demonstrated for the first time for continuous wave, tunable and mode-locked regimes. For comparison, the laser experiments have also been performed in the same configuration with the reference forsterite single crystal solely doped by chromium. The aim of scandium codoping is to inhibit the formation of parasitic trivalent chromium in the crystal. The crystal with scandium demonstrates a wider tuning range, lower lasing threshold and wider mode-locked lasing spectrum than those of the reference crystal, although the total lasing efficiency achieved by both crystals is nearly the same. The obtained results are discussed.

Intrinsic polarization control in rectangular GaN nanowire lasers

DOE PAGES

Li, Changyi; Liu, Sheng; Luk, Ting S.; ...

2016-02-01

In this study, we demonstrate intrinsic, linearly polarized lasing from single GaN nanowires using cross-sectional shape control. A two-step top-down fabrication approach was employed to create straight nanowires with controllable rectangular cross-sections. A clear lasing threshold of 444kW/cm 2 and a narrow spectral line width of 0.16 nm were observed under optical pumping at room temperature, indicating the onset of lasing. The polarization was along the short dimension (y-direction) of the nanowire due to the higher transverse confinement factors for y-polarized transverse modes resulting from the rectangular nanowire cross-section. The results show that cross-sectioned shape control can enable inherent controlmore » over the polarization of nanowire lasers without additional environment requirements, such as placement onto lossy substrates.« less

On-chip tunable optofluidic dye laser

NASA Astrophysics Data System (ADS)

Cai, Zengyan; Shen, Zhenhua; Liu, Haigang; Yue, Huan; Zou, Yun; Chen, Xianfeng

2016-11-01

We demonstrate a chip-scale tunable optofluidic dye laser with Au-coated fibers as microcavity. The chip is fabricated by soft lithography. When the active region is pumped, a relatively low threshold of 6.7 μJ/mm2 is realized with multimode emission due to good confinement of the cavity mirrors, long active region, as well as total reflectivity. It is easy to tune the lasing emission wavelength by changing the solvent of laser dye. In addition, the various intensity ratios of multicolor lasing can be achieved by controlling flow rates of two fluid streams carried with different dye molecules. Furthermore, the convenience in fabrication and directional lasing emission outcoupled by the fiber make the tunable optofluidic dye laser a promising underlying coherent light source in the integrated optofluidic systems.

Nonlinear Spectral Singularity and Laser Output Intensity for the TE and TM Modes

NASA Astrophysics Data System (ADS)

Ghaemidizicheh, Hamed; Mostafazadeh, Ali

The nonlinear spectral singularity arising from a Kerr nonlinearity is explored in. This reference studies the effect of nonlinearity in Lasing condition and shows that Kerr nonlinearity with spectral singularity for a normally incident wave provides an explanation of lasing at gain coefficient g. Lasing occurs when it exceeds threshold gain g0. For oblique waves, Ref. looks at the behavior of threshold gain coefficient g0 which is given by the condition that there is a linear spectral singularity. We investigated imposing the condition of the existence of nonlinear spectral singularity in the TE / TM modes of a mirrorless slab of gain materials and studied the θ-dependence of intensity. Supported by TUBITAK Project No: 114F357 and by the Turkish Academy of Science (TUBA).

Ho3+ doped fluoroaluminate glass fibers for 2.9 µm lasing

NASA Astrophysics Data System (ADS)

Jia, S. J.; Jia, Z. X.; Yao, C. F.; Wang, S. B.; Jiang, H. W.; Zhang, L.; Feng, Y.; Qin, G. S.; Ohishi, Y.; Qin, W. P.

2018-01-01

Ho3+ doped fluoroaluminate glass fibers based on chemically durable AlF3-BaF2-YF3-PbF2-MgF2-CaF2 glasses are fabricated by using a rod-in-tube method. By using an 84 cm long Ho3+-doped fluoroaluminate glass fiber as the gain medium and a 1120 nm fiber laser as the pump source, lasing at 2868 nm is obtained, the maximum unsaturated power is about 57 mW for a pump power of 1224 mW, and the corresponding slope efficiency is ~5.1%. The effect of the fiber length on lasing at 2868 nm is also investigated. Our results show that Ho3+-doped fluoroaluminate glass fibers are promising gain media for 2.9 µm laser applications.

LaRC results on nuclear pumped noble gas lasers

NASA Technical Reports Server (NTRS)

Deyoung, R. J.

1979-01-01

The recent experiment and theoretical results obtained for noble gas nuclear laser systems are presented. It is shown that the noble gas lasers are among the easiest systems to pump by nuclear excitation and as a result, all of the noble gases except He have lased under nuclear excitation. The noble gas systems are not ideal for high-power applications but they do give valuable insight into the operation and pumping mechanisms associated with nuclear lasers. At present, the Ar-Xe system is the best noble gas candidate for (U-235)F6 pumping. It appears that the quenching of Ar-Xe lasing is a result of the fluorine and not the uranium or fission fragments themselves. Thus, to achieve lasing with UF6, a fluorine compatible system must be found.

830-nm Polarization Controlled Lasing of InGaAs Quantum Wire Vertical-Cavity Surface-Emitting Lasers Grown on (775)B GaAs Substrates by Molecular Beam Epitaxy

NASA Astrophysics Data System (ADS)

Higuchi, Yu; Osaki, Shinji; Sasahata, Yoshifumi; Kitada, Takahiro; Shimomura, Satoshi; Ogura, Mutsuo; Hiyamizu, Satoshi

2007-02-01

We report the first demonstration of room temperature (RT) current injection lasing of vertical-cavity surface-emitting lasers (VCSELs), with self-organized InGaAs/(GaAs)6(AlAs)1 quantum wires (QWRs) in their active region, grown on (775)B-oriented GaAs substrates by molecular beam epitaxy. A (775)B InGaAs QWR-VCSEL with an aperture diameter of 4 μm lased at a wavelength of 829.7 nm and a threshold current of 0.7 mA at RT. The light output was linearly polarized in the direction parallel to the QWRs due to optical anisotropy of the self-organized (775)B InGaAs QWRs.

Continuous-wave lasing in colloidal quantum dot solids enabled by facet-selective epitaxy.

PubMed

Fan, Fengjia; Voznyy, Oleksandr; Sabatini, Randy P; Bicanic, Kristopher T; Adachi, Michael M; McBride, James R; Reid, Kemar R; Park, Young-Shin; Li, Xiyan; Jain, Ankit; Quintero-Bermudez, Rafael; Saravanapavanantham, Mayuran; Liu, Min; Korkusinski, Marek; Hawrylak, Pawel; Klimov, Victor I; Rosenthal, Sandra J; Hoogland, Sjoerd; Sargent, Edward H

2017-04-06

Colloidal quantum dots (CQDs) feature a low degeneracy of electronic states at the band edges compared with the corresponding bulk material, as well as a narrow emission linewidth. Unfortunately for potential laser applications, this degeneracy is incompletely lifted in the valence band, spreading the hole population among several states at room temperature. This leads to increased optical gain thresholds, demanding high photoexcitation levels to achieve population inversion (more electrons in excited states than in ground states-the condition for optical gain). This, in turn, increases Auger recombination losses, limiting the gain lifetime to sub-nanoseconds and preventing steady laser action. State degeneracy also broadens the photoluminescence linewidth at the single-particle level. Here we demonstrate a way to decrease the band-edge degeneracy and single-dot photoluminescence linewidth in CQDs by means of uniform biaxial strain. We have developed a synthetic strategy that we term facet-selective epitaxy: we first switch off, and then switch on, shell growth on the (0001) facet of wurtzite CdSe cores, producing asymmetric compressive shells that create built-in biaxial strain, while still maintaining excellent surface passivation (preventing defect formation, which otherwise would cause non-radiative recombination losses). Our synthesis spreads the excitonic fine structure uniformly and sufficiently broadly that it prevents valence-band-edge states from being thermally depopulated. We thereby reduce the optical gain threshold and demonstrate continuous-wave lasing from CQD solids, expanding the library of solution-processed materials that may be capable of continuous-wave lasing. The individual CQDs exhibit an ultra-narrow single-dot linewidth, and we successfully propagate this into the ensemble of CQDs.

Metal atom oxidation laser

DOEpatents

Jensen, R.J.; Rice, W.W.; Beattie, W.H.

1975-10-28

A chemical laser which operates by formation of metal or carbon atoms and reaction of such atoms with a gaseous oxidizer in an optical resonant cavity is described. The lasing species are diatomic or polyatomic in nature and are readily produced by exchange or other abstraction reactions between the metal or carbon atoms and the oxidizer. The lasing molecules may be metal or carbon monohalides or monoxides. (auth)

Mechanical properties and molecular structure analysis of subsurface dentin after Er:YAG laser irradiation.

PubMed

He, Zhengdi; Chen, Lingling; Hu, Xuejuan; Shimada, Yasushi; Otsuki, Masayuki; Tagami, Junji; Ruan, Shuangchen

2017-10-01

The purpose of this study was to evaluate the chemical and mechanical modifications in subsurface dentin layer after Er: YAG (Erbium-Yttrium Aluminium Garnet) laser irradiation, as the guidance of new dental restorative materials specific for laser irradiated dentin. Dentin disks obtained from extracted human molars were prepared and exposed to a single pulse Er:YAG laser irradiation at 80mJ/pulse. After laser irradiation the mechanical and chemical characteristics of intertubular dentin in subsurface layer were studied using nanoindentation tester and micro-Raman spectromy (μ-RS). The dentin 5-50µm depth beneath the lased surface was determined as testing area. Two-way analysis of variance (ANOVA) were used to compare the mechanical values between lased and untreated subsurface dentin (P = 0.05). A laser affected subsurface dentin layer after Er:YAG laser treatment is present. The laser irradiation is considered to decrease the mechanical properties in the superficial subsurface layer (<15µm deep). There was no significant difference in nanohardness and Young's modulus between lased subsurface dentin and untreated dentin (p > 0.05) under the depth of 15µm. However, the dentin at 5µm and 10µm depth beneath the lased surface exhibited significantly lower (~ 47.8% and ~ 33.6% respectively) hardness (p < 0.05). Er:YAG laser irradiation affected both mineral and organic components in subsurface dentin layer, a higher degree of crystallinity and reduced organic compounds occurred in the lased subsurface dentin. Under the tested laser parameters, Er:YAG laser irradiation causes lower mechanical values and reduction of organic components in subsurface dentin, which has deleterious effects on resin adhesion to this area. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Effects of laser procedure for female urodynamic stress incontinence on pad weight, urodynamics, and sexual function.

PubMed

Tien, Yi-Wen; Hsiao, Sheng-Mou; Lee, Chien-Nan; Lin, Ho-Hsiung

2017-03-01

The impact of the IncontiLase TM procedure on lower urinary tract symptoms (LUTS) remains unclear. Our aim was to evaluate the effects of the IncontiLase TM procedure for urodynamic stress incontinence (USI). All consecutive women with USI prospectively underwent the IncontiLase TM procedure. Urodynamic studies, pad testing, LUTS, and sexual function questionnaires were assessed before and after treatment. Thirty-five women underwent the IncontiLase TM procedure. Among the 28 women with baseline pad weights >1 g, 11 (39.3 %) were objectively cured and 11 (39.3 %) improved. Among the 18 women with mild USI (i.e., baseline pad weight 1-10 g), nine (50 %) were cured and five (27.8 %) improved. Among ten women with baseline pad weight >10 g, two (20 %) were cured and six (60 %) improved. Among the 32 women with complete questionnaire data at 6 months, seven (21.9 %) were subjectively cured, and four (12.5 %) improved. Regarding LUTS, the majority of domains on the King's Health Questionnaire and female sexual desire and function exhibited significant improvements. Forty percent (12/30) of the partners of these patients felt their sexual function had improved at 6 months. Nonetheless, urodynamic values did not differ across the timeline. The effect of the IncontiLase TM procedure for mild USI was moderate at 6-month follow-up but was not effective for pad weight >10 g. Moreover, it improved LUTS, quality of life, QoL, and sexual function of both partners. Further studies should be performed to assess long-term sustained efficacy.

Lasing eigenvalue problems: the electromagnetic modelling of microlasers

NASA Astrophysics Data System (ADS)

Benson, Trevor; Nosich, Alexander; Smotrova, Elena; Balaban, Mikhail; Sewell, Phillip

2007-02-01

Comprehensive microcavity laser models should account for several physical mechanisms, e.g. carrier transport, heating and optical confinement, coupled by non-linear effects. Nevertheless, considerable useful information can still be obtained if all non-electromagnetic effects are neglected, often within an additional effective-index reduction to an equivalent 2D problem, and the optical modes viewed as solutions of Maxwell's equations. Integral equation (IE) formulations have many advantages over numerical techniques such as FDTD for the study of such microcavity laser problems. The most notable advantages of an IE approach are computational efficiency, the correct description of cavity boundaries without stair-step errors, and the direct solution of an eigenvalue problem rather than the spectral analysis of a transient signal. Boundary IE (BIE) formulations are more economic that volume IE (VIE) ones, because of their lower dimensionality, but they are only applicable to the constant cavity refractive index case. The Muller BIE, being free of 'defect' frequencies and having smooth or integrable kernels, provides a reliable tool for the modal analysis of microcavities. Whilst such an approach can readily identify complex-valued natural frequencies and Q-factors, the lasing condition is not addressed directly. We have thus suggested using a Muller BIE approach to solve a lasing eigenvalue problem (LEP), i.e. a linear eigenvalue solution in the form of two real-valued numbers (lasing wavelength and threshold information) when macroscopic gain is introduced into the cavity material within an active region. Such an approach yields clear insight into the lasing thresholds of individual cavities with uniform and non-uniform gain, cavities coupled as photonic molecules and cavities equipped with one or more quantum dots.

Amplified spontaneous emission in phenylethylammonium methylammonium lead iodide quasi-2D perovskites.

PubMed

Leyden, Matthew R; Matsushima, Toshinori; Qin, Chuanjiang; Ruan, Shibin; Ye, Hao; Adachi, Chihaya

2018-06-06

Organo-metal-halide perovskites are a promising set of materials for optoelectronic applications such as solar cells, light emitting diodes and lasers. Perovskite thin films have demonstrated amplified spontaneous emission thresholds as low as 1.6 μJ cm-2 and lasing thresholds as low as 0.2 μJ cm-2. Recently the performance of perovskite light emitting diodes has rapidly risen due to the formation of quasi 2D films using bulky ligands such as phenylethylammonium. Despite the high photoluminescent yield and external quantum efficiency of quasi 2D perovskites, few reports exist on amplified spontaneous emission. We show within this report that the threshold for amplified spontaneous emission of quasi 2D perovskite films increases with the concentration of phenylethylammonium. We attribute this increasing threshold to a charge transfer state at the PEA interface that competes for excitons with the ASE process. Additionally, the comparatively slow inter-grain charge transfer process cannot significantly contribute to the fast radiative recombination in amplified spontaneous emission. These results suggest that relatively low order PEA based perovskite films that are suitable for LED applications are not well suited for lasing applications. However high order films were able to maintain their low threshold values and may still benefit from improved stability.

Monolithic dye laser amplifier

DOEpatents

Kuklo, T.C.

1993-03-30

A fluid dye laser amplifier for amplifying a dye beam by pump beams has a channel structure defining a channel through which a laseable fluid flows and the dye and pump beams pass transversely to one another through a lasing region. The channel structure is formed with two pairs of mutually spaced-apart and mutually confronting glass windows, which are interlocked and make surface-contacts with one another and surround the lasing region. One of the glass window pairs passes the dye beam and the other passes the pump beams therethrough and through the lasing region. Where these glass window pieces make surface-contacts, glue is used to join the pieces together to form a monolithic structure so as to prevent the dye in the fluid passing through the channel from entering the space between the mutually contacting glass window pieces.

Monolithic dye laser amplifier

DOEpatents

Kuklo, Thomas C.

1993-01-01

A fluid dye laser amplifier for amplifying a dye beam by pump beams has a channel structure defining a channel through which a laseable fluid flows and the dye and pump beams pass transversely to one another through a lasing region. The channel structure is formed with two pairs of mutually spaced-apart and mutually confronting glass windows, which are interlocked and make surface-contacts with one another and surround the lasing region. One of the glass window pairs passes the dye beam and the other passes the pump beams therethrough and through the lasing region. Where these glass window pieces make surface-contacts, glue is used to join the pieces together to form a monolithic structure so as to prevent the dye in the fluid passing through the channel from entering the space between the mutually contacting glass window pieces.

Growth of GaN micro/nanolaser arrays by chemical vapor deposition.

PubMed

Liu, Haitao; Zhang, Hanlu; Dong, Lin; Zhang, Yingjiu; Pan, Caofeng

2016-09-02

Optically pumped ultraviolet lasing at room temperature based on GaN microwire arrays with Fabry-Perot cavities is demonstrated. GaN microwires have been grown perpendicularly on c-GaN/sapphire substrates through simple catalyst-free chemical vapor deposition. The GaN microwires are [0001] oriented single-crystal structures with hexagonal cross sections, each with a diameter of ∼1 μm and a length of ∼15 μm. A possible growth mechanism of the vertical GaN microwire arrays is proposed. Furthermore, we report room-temperature lasing in optically pumped GaN microwire arrays based on the Fabry-Perot cavity. Photoluminescence spectra exhibit lasing typically at 372 nm with an excitation threshold of 410 kW cm(-2). The result indicates that these aligned GaN microwire arrays may offer promising prospects for ultraviolet-emitting micro/nanodevices.

Thermal effects and antibacterial properties of energy levels required to sterilize stained root canals with an Nd:YAG laser.

PubMed

Ramsköld, L O; Fong, C D; Strömberg, T

1997-02-01

Thermal effects and antibacterial properties of an Nd:YAG laser were studied to establish clinically safe levels of energy to deliver into the root canal and to determine the energy level needed to sterilize infected root canals. The results indicate that lasing cycles of 3 J-s for 15 s followed by a 15-s recovery interval can be continued for prolonged periods without risk of thermal damage to surrounding tissues. In vitro lasing of root canals inoculated with dark stained bacteria showed that two such lasing cycles sterilized only two out of eight canals, whereas when four cycles were used seven out of eight canals were sterilized. Guidelines for energy levels in endodontic Nd:YAG laser work are discussed, and base data for calculating appropriate energy levels are given.

Evaluation of thermal cooling mechanisms for laser application to teeth.

PubMed

Miserendino, L J; Abt, E; Wigdor, H; Miserendino, C A

1993-01-01

Experimental cooling methods for the prevention of thermal damage to dental pulp during laser application to teeth were compared to conventional treatment in vitro. Pulp temperature measurements were made via electrical thermistors implanted within the pulp chambers of extracted human third molar teeth. Experimental treatments consisted of lasing without cooling, lasing with cooling, laser pulsing, and high-speed dental rotary drilling. Comparisons of pulp temperature elevation measurements for each group demonstrated that cooling by an air and water spray during lasing significantly reduced heat transfer to dental pulp. Laser exposures followed by an air and water spray resulted in pulp temperature changes comparable to conventional treatment by drilling. Cooling by an air water spray with evacuation appears to be an effective method for the prevention of thermal damage to vital teeth following laser exposure.

Spectral engineering for circular-side square microlasers.

PubMed

Weng, Hai-Zhong; Yang, Yue-De; Xiao, Jin-Long; Hao, You-Zeng; Huang, Yong-Zhen

2018-04-16

Spectral engineering has been demonstrated for the circular-side square microlasers with an output waveguide butt-coupled to one vertex. By carefully optimizing deformation parameter and waveguide connection angle, undesired high-order transverse modes are suppressed while the mode Q factors and the transverse-mode intervals are enhanced simultaneously for the low-order transverse modes. Dual-mode lasing with pure lasing spectra is realized experimentally for the circular-side square microlasers with side lengths of 16 μm, and the transverse mode intervals can be adjusted from 0.54 to 5.4 nm by changing the deformation parameter. Due to the enhanced mode confinement, single-mode lasing with a side-mode suppression-ratio of 36 dB is achieved for a 10μm-side-length circular-side square microlaser with a 1.5μm-wide waveguide.

Optimization of rare-earth-doped fluorides for infrared lasers

NASA Astrophysics Data System (ADS)

Peterson, Rita Dedomenico

2000-11-01

The rare-earth-doped fluoride crystals Tm,Dy:BaY2F8 (Tm,Dy:BYF), Yb,Pr:NaYF4 (Yb,Pr:NYF), and Nd:NYF show considerable promise as infrared laser materials, operating at 3 μm, 1.3 μm, and 1.06 μm respectively. Lasing has been reported previously on all three ionic transitions, but not in these crystals. Optimization of these materials for laser applications requires a more complete spectroscopic characterization than is currently available, particularly with regard to the key parameters of fluorescence lifetime and stimulated emission cross section. To further the optimization process, polarized absorption and emission have been measured for Tm,Dy:BYF, Yb,Pr:NYF, and Nd:NYF, and relevant fluorescence lifetimes have been measured or estimated. For Tm,Dy:BYF and Yb,Pr:NYF which rely upon sensitization, energy transfer parameters were calculated. Results were used in a mathematical model to determine the conditions in which lasing may be obtained. The long upper laser level lifetime in Tm,Dy:BYF translates into low threshold pump intensity, but the ability to reach threshold depends strongly on active ion concentration. The short lifetime in Yb,Pr:NYF leads to much higher threshold pump intensities, but lasing is still attainable if resonator loss is minimized. In Nd:NYF lasing was demonstrated, with a maximum of 60 mW output from an absorbed pump power of 345 mW, and a slope efficiency of 21%. Thresholds were high owing to resonator losses near 9%. Two chief issues involving the optimization of these laser materials were identified and explored. First, identification of the orientation for which emission cross section is highest is complicated in Tm,Dy:BYF by the presence of strong magnetic dipole radiation on the 3 μm transition. This effect makes it necessary to account for the polarization of both the electric and magnetic fields of the emitted radiation when determining an optimal crystal orientation, an accounting further complicated by the low symmetry of the monoclinic BYF host crystal. Second, the effect of host crystal on fluorescence lifetime was considered by comparing lifetime values for the same ionic manifolds in BYF, NYF, and other host crystals. NYF has especially low phonon energies, which leads to longer lifetimes on the longer wavelength transitions which are susceptible to multiphonon relaxation. This advantage is especially needed for lasing at 1.3 μm in Pr where the upper level lifetime is very short. On the shorter wavelength transitions in Tm and Nd, however, the role of phonons is negligible and lifetimes are somewhat shorter than in other fluoride hosts.

Excimer laser with fluoropolymer lining

DOEpatents

Sze, Robert C.

1982-01-01

A cavity formed of Teflon to provide extended static fill lifetimes for gases containing halogens. A double cavity configuration provides structural integrity to the inner Teflon cavity by maintaining an identical multi-atmospheric pressure within the outer structural cavity to minimize tension on the Teflon inner cavity. Use of a quantity of the lasing gas in the outer cavity or a constituent of that gas minimizes contamination of the lasing gas.

A Nanowire-Based Plasmonic Quantum Dot Laser.

PubMed

Ho, Jinfa; Tatebayashi, Jun; Sergent, Sylvain; Fong, Chee Fai; Ota, Yasutomo; Iwamoto, Satoshi; Arakawa, Yasuhiko

2016-04-13

Quantum dots enable strong carrier confinement and exhibit a delta-function like density of states, offering significant improvements to laser performance and high-temperature stability when used as a gain medium. However, quantum dot lasers have been limited to photonic cavities that are diffraction-limited and further miniaturization to meet the demands of nanophotonic-electronic integration applications is challenging based on existing designs. Here we introduce the first quantum dot-based plasmonic laser to reduce the cross-sectional area of nanowire quantum dot lasers below the cutoff limit of photonic modes while maintaining the length in the order of the lasing wavelength. Metal organic chemical vapor deposition grown GaAs-AlGaAs core-shell nanowires containing InGaAs quantum dot stacks are placed directly on a silver film, and lasing was observed from single nanowires originating from the InGaAs quantum dot emission into the low-loss higher order plasmonic mode. Lasing threshold pump fluences as low as ∼120 μJ/cm(2) was observed at 7 K, and lasing was observed up to 125 K. Temperature stability from the quantum dot gain, leading to a high characteristic temperature was demonstrated. These results indicate that high-performance, miniaturized quantum dot lasers can be realized with plasmonics.

Terahertz quantum cascade laser with an X-valley-based injector

NASA Astrophysics Data System (ADS)

Roy, Mithun; Talukder, Muhammad Anisuzzaman

2017-04-01

We present a novel terahertz (THz) quantum cascade laser (QCL) design where Γ-valley states are used for lasing transition and X-valley states—in particular, Xz-states—are used as injector subbands. Since the lasing states in our proposed structure are populated and depopulated mainly through the interface roughness assisted Γ-Xz electron scattering, we present a model to describe this intervalley carrier transport. In the injector region of the proposed THz QCL, we use a quaternary AlGaAsP material to introduce tensile strain, which plays a crucial role in increasing the gain. To compensate the strain per period, we propose to grow the periodic heterostructure on a GaAs 0.94 P 0.06 virtual substrate. To simulate the carrier transport and hence calculate the gain and lasing performance of the proposed THz QCL, we use a simplified density matrix formalism that considers resonant tunneling, dephasing, and the important intersubband scattering mechanisms. Since electron temperature significantly varies from lattice temperature for QCLs, we take their difference into account using the kinetic energy balance method. We show that the proposed structure is capable of lasing up to a maximum lattice temperature of ˜119 K at 4.8 THz. For future improvements of the device, we identify major performance-degrading factors of the proposed design.

Reproducibility of flap thickness with IntraLase FS and Moria LSK-1 and M2 microkeratomes.

PubMed

Talamo, Jonathan H; Meltzer, Jeremy; Gardner, John

2006-06-01

To compare flap thickness reproducibility of the femtosecond laser and two mechanical microkeratomes. Flap thickness for all eyes was measured as the difference between the preoperative (day of surgery) full corneal thickness and post-flap creation central stromal bed thickness using ultrasonic pachymetry. Flap thickness values produced by three different microkeratome systems were compared for accuracy and reproducibility. For 99 flaps created using the IntraLase FS laser with an intended thickness of 110 microm, the mean achieved thickness was 119 +/- 12 microm (range: 82 to 149 microm). In 100 eyes treated with the Moria LSK-1 microkeratome with an intended flap thickness of 160 microm, the mean achieved thickness was 130 +/- 19 microm (range: 71 to 186 microm). In 135 eyes treated with the Moria M2 microkeratome with an intended flap thickness of 130 microm, mean thickness was 142 +/- 24 microm (range: 84 to 203 microm). The standard deviation and range of corneal flap thickness created with the IntraLase FS laser was significantly smaller than either mechanical microkeratome (P < .0001). When compared to two commonly used mechanical microkeratomes, mean achieved flap thickness was more reproducible with the IntraLase FS laser, reducing the comparative risk of overly thick flaps.

Temperature changes across CO2-lased dentin during multiple exposures

NASA Astrophysics Data System (ADS)

Zakariasen, Kenneth L.; Barron, Joseph R.; Boran, Thomas L.

1990-06-01

The literature increasingly indicates that lasers will have a multitude of applications for dental hard tissue procedures, e.g. preventive therapy, caries removal, laser etching and endodontic therapy. However, it is critical that such laser therapies avoid the production of heat levels which will be damaging to the surrounding vital tissues, such as the dental pulp and periodontal tissues. Our preliminary research on temperature changes across C02 lased dentin indicated that for single preventive therapeutic exposures (1.2 W., 0. 1 sec., 1.0 mm focal spot) the mean temperature rise across 350 j.tm of dentin was 0.57 0C while across 1000 .tm of dentin the mean rise was only 0.18 °C. Further research utilizing multiple preventive therapeutic exposures (1.2 W., 0. 1 sec., 1.0 mm focal spot, 3 x 1.0 sec. intervals) showed mean temperature elevations of 1.56 0C across 350 m of dentin and 0.66 O across 1000 xm of dentin. While these temperature elevations, which would be associated with preventive therapy, are very low and would be biologically acceptable, it must be noted that exposures of higher intensities are required to fuse enamel and porcelain, or remove decay. This current research investigates temperature elevations which occuT during C02 lasing utilizing the following exposure parameters: 8.0 W., 1.0 mm focal spot, 0.1 sec. exposures, 2 or 4 exposures per site pulsed 1.0 sec. apart. Three dentin thicknesses were utilized, i.e. 1000 jim, 1500 p.tm and 2000 .tm. Four sections of each thickness were utilized with four exposure sites per specimen (2 with 2 exposures, 2 with 4 exposures). All dentin sections were prepared from non-carious third molars using a hard tissue microtome. A thermistor was placed on the dentin surface opposite each lased site and temperature changes were recorded for approximately 50 sec. following lasing. Mean temperature elevations ranged from a high of 3.07 C for the 1000 xm section utilizing four exposures to a low of 0.37 0C for the 2000 m section utilizing two exposures. Analysis of Variance (p < .0001) and Duncan's Multiple Range Test (p =.05) indicated significant differences existed among the mean temperature elevations observed. While significant differences in temperature elevation can be observed both by numbers of exposures and by dentin thickness, it would appear that, under the conditions of this study, the temperature changes across CO2 lased dentin are all relatively low. It should be reiterated that the lasing parameters used in this study are far in excess of those necessary for preventive applications and are, in fact, in the range of exposures which will fuse enamel and dental porcelain, or remove dental caries. The modest temperature elevations observed, combined with the relatively severe exposure parameters utilized on thin sections of dentin, demonstrate the effective protective barrier which dentin provides for the dental pulp relative to heat damage from C02 lasing.

Vertical cavity surface emitting lasers from all-inorganic perovskite quantum dots

NASA Astrophysics Data System (ADS)

Sun, Handong; Wang, Yue; Li, Xiaoming; Zeng, Haibo

We report the breakthrough in realizing the challenging while practically desirable vertical cavity surface emitting lasers (VCSELs) based on the CsPbX3 inorganic perovskite nanocrystals (IPNCs). These laser devices feature record low threshold (9 µJ/cm2), unidirectional output (beam divergence of 3.6º) and superb stability. We show that both single-mode and multimode lasing operation are achievable in the device. In contrast to traditional metal chacogenide colloidal quantum dots based lasers where the pump thresholds for the green and blue wavelengths are typically much higher than that of the red, these CsPbX3 IPNC-VCSEL devices are able to lase with comparable thresholds across the whole visible spectral range, which is appealing for achieving single source-pumped full-color lasers. We further reveal that these lasers can operate in quasi-steady state regime, which is very practical and cost-effective. Given the facile solution processibility, our CsPbX3 IPNC-VCSEL devices may hold great potential in developing low-cost yet high-performance lasers, promising in revolutionizing the vacuum-based epitaxial semiconductor lasers.

Microhardness and morphological changes induced by Nd:Yag laser on dental enamel: an in vitro study.

PubMed

Bedini, Rossella; Manzon, Licia; Fratto, Giovanni; Pecci, Raffaella

2010-01-01

The aim of this work was a scanning electron microscopy (SEM) evaluation of the hardness and morphological changes of enamel irradiated by neodymium: yttrium aluminium garnet (Nd:YAG) laser with different energy levels. Twenty-eight human teeth samples were divided into 4 groups: control, where enamel surface was not lased, and 3 test treated with 3 different levels of energy power 0.6, 1.2 and 2.4 Watt, respectively. In each group, 5 samples underwent Vickers micro-hardness test and 2 samples were processed for SEM. No significant differences between treated and non treated samples were found by micro-hardness test. However, by SEM, test samples showed a rougher enamel surface than control. Specifically, the 0.6 Watt treated samples showed vertical scratches and glass-like areas, while in the other 2 groups enamel surface was covered by craters and cracks. These findings suggest that enamel should be lased at a low energy level to preserve its integrity and reduce demineralization, and thus for dental caries prevention purposes; while high energy level creates a retentive surface suitable for sealant or composite anchorage.

Explosives Detection in a Lasing Plasmon Nanocavity

DTIC Science & Technology

2014-08-01

plasmonic sensors7,13–18 with 2,4-dinitrotoluene and ammonium nitrate . The selectivity between 2,4-dinitrotoluene, ammonium nitrate and nitrobenzene is on a...ammonium nitrate . The selectivity between 2,4-dinitrotoluene, ammoniumnitrate and nitrobenzene is on a par with other state-of-the-art explosives... nitrate (AN) and nitrobenzene (NB). Air was used both to dilute them and as the background reference. Figure 4a–c presents con- tinuous traces of lasing

Spatio-temporal Theory of Lasing Action in Optically-Pumped Rotationally Excited Molecular Gases

DTIC Science & Technology

2011-04-11

17. A. E. Siegman , Lasers (Univ. Science Books, 1986). 18. R. Bansal (ed.), Handbook of Engineering Electromagnetics (Marcel Dekker, Inc., 2004). 19... laser emission from optically-pumped rota- tionally excited molecular gases confined in a metallic cavity. To this end, we have developed a...the operation of this class of lasers . The effect on the main lasing features of the spatial variation of the electric field intensity and the ohmic

Narrow linewidth short cavity Brillouin random laser based on Bragg grating array fiber and dynamical population inversion gratings

NASA Astrophysics Data System (ADS)

Popov, S. M.; Butov, O. V.; Chamorovski, Y. K.; Isaev, V. A.; Mégret, P.; Korobko, D. A.; Zolotovskii, I. O.; Fotiadi, A. A.

2018-06-01

We report on random lasing observed with 100-m-long fiber comprising an array of weak FBGs inscribed in the fiber core and uniformly distributed over the fiber length. Extended fluctuation-free oscilloscope traces highlight power dynamics typical for lasing. An additional piece of Er-doped fiber included into the laser cavity enables a stable laser generation with a linewidth narrower than 10 kHz.

Measuring milk fat content by random laser emission

NASA Astrophysics Data System (ADS)

Abegão, Luis M. G.; Pagani, Alessandra A. C.; Zílio, Sérgio C.; Alencar, Márcio A. R. C.; Rodrigues, José J.

2016-10-01

The luminescence spectra of milk containing rhodamine 6G are shown to exhibit typical signatures of random lasing when excited with 532 nm laser pulses. Experiments carried out on whole and skim forms of two commercial brands of UHT milk, with fat volume concentrations ranging from 0 to 4%, presented lasing threshold values dependent on the fat concentration, suggesting that a random laser technique can be developed to monitor such important parameter.

Measuring milk fat content by random laser emission.

PubMed

Abegão, Luis M G; Pagani, Alessandra A C; Zílio, Sérgio C; Alencar, Márcio A R C; Rodrigues, José J

2016-10-12

The luminescence spectra of milk containing rhodamine 6G are shown to exhibit typical signatures of random lasing when excited with 532 nm laser pulses. Experiments carried out on whole and skim forms of two commercial brands of UHT milk, with fat volume concentrations ranging from 0 to 4%, presented lasing threshold values dependent on the fat concentration, suggesting that a random laser technique can be developed to monitor such important parameter.

Plasma Dopamine-Beta-Hydroxylase as an Index of Peripheral Noradrenergic Activity

DTIC Science & Technology

1981-08-17

Hydroxy lase A c t i v i t y of Monkey Plasma wi th Age. Exper ient ia (Basel ) 1976, 32:834-835 118. Kato, T . ; Waki , Y . ; Nagatsu, T . ; Ohn ish i...Kato , T . ; Waki , Y . ; Nagatsu, T . ; Ohn i sh i , T . : A Simple and Sens i t ive Assay f o r Dopamine-Beta-Hydroxy lase A c t i v i t y by Dual

THE FIRST LASING OF 193 NM SASE, 4TH HARMONIC HGHG AND ESASE AT THE NSLS SDL.

DOE Office of Scientific and Technical Information (OSTI.GOV)

WANG, X.J.; SHEN Y.; WATANABE, T.

2006-08-28

The first lasing of three types of single-pass high-gain FELs, SASE at 193 nm, 4th harmonic HGHG at 199 nm and ESASE at the Source Development Lab (SDL) of Brookhaven National Laboratory (BNL) is reported. The saturation of 4th harmonic HGHG and ESASE FELs was observed. We also observed the spectral broadening and instability of the 4th harmonic HGHG.

Hollow Core Optical Fiber Gas Lasers: Toward Novel and Practical Systems in Fused Silica

DTIC Science & Technology

2017-05-18

Hollow core Optically pumped Fiber Gas LASer’s (HOFGLAS’s) based on population inversion combine advantages of fiber lasers such as long interaction...polarization dependent fiber properties. Preliminary experiments were performed toward simultaneous lasing in the visible and near infrared; lasing in...words) Hollow core Optically pumped Fiber Gas LASer’s (HOFGLAS’s) based on population inversion combine advantages of fiber lasers such as long

Tailoring Eigenmodes at Spectral Singularities in Graphene-based PT Systems.

PubMed

Zhang, Weixuan; Wu, Tong; Zhang, Xiangdong

2017-09-12

The spectral singularity existing in PT-synthetic plasmonic system has been widely investigated. Only lasing-mode can be excited resulting from the passive characteristic of metallic materials. Here, we investigated the spectral singularity in the hybrid structure composed of the photoexcited graphene and one-dimensional PT-diffractive grating. In this system, both lasing- and absorption-modes can be excited with the surface conductivity of photoexcited graphene being loss and gain, respectively. Remarkably, the spectral singularity will disappear with the optically pumped graphene to be lossless. In particular, we find that spectral singularities can exhibit symmetry-modes, when the loss and gain of the grating is unbalanced. Meanwhile, by tuning the loss (gain) of graphene and non-PT diffraction grating, lasing- and absorption-modes can also be excited. We hope that tunable optical modes at spectral singularities can have some applications in designing novel surface-enhanced spectroscopies and plasmon lasers.

Lasing in topological edge states of a one-dimensional lattice

NASA Astrophysics Data System (ADS)

St-Jean, P.; Goblot, V.; Galopin, E.; Lemaître, A.; Ozawa, T.; Le Gratiet, L.; Sagnes, I.; Bloch, J.; Amo, A.

2017-10-01

Topology describes properties that remain unaffected by smooth distortions. Its main hallmark is the emergence of edge states localized at the boundary between regions characterized by distinct topological invariants. Because their properties are inherited from the topology of the bulk, these edge states present a strong immunity to distortions of the underlying architecture. This feature offers new opportunities for robust trapping of light in nano- and micrometre-scale systems subject to fabrication imperfections and environmentally induced deformations. Here, we report lasing in such topological edge states of a one-dimensional lattice of polariton micropillars that implements an orbital version of the Su-Schrieffer-Heeger Hamiltonian. We further demonstrate that lasing in these states persists under local deformations of the lattice. These results open the way to the implementation of chiral lasers in systems with broken time-reversal symmetry and, when combined with polariton interactions, to the study of nonlinear phenomena in topological photonics.

Continuous-wave lasing from InP/InGaAs nanoridges at telecommunication wavelengths

NASA Astrophysics Data System (ADS)

Han, Yu; Li, Qiang; Zhu, Si; Ng, Kar Wei; Lau, Kei May

2017-11-01

We report continuous-wave lasing from InP/InGaAs nanoridges grown on a patterned (001) Si substrate by aspect ratio trapping. Multi-InGaAs ridge quantum wells inside InP nanoridges are designed as active gain materials for emission in the 1500 nm band. The good crystalline quality and optical property of the InGaAs quantum wells are attested by transmission electron microscopy and microphotoluminescence measurements. After transfer of the InP/InGaAs nanoridges onto a SiO2/Si substrate, amplified Fabry-Perot resonant modes at room temperature and multi-mode lasing behavior in the 1400 nm band under continuous-wave optical pumping at 4.5 K are observed. This result thus marks an important step towards integrating InP/InGaAs nanolasers directly grown on microelectronic standard (001) Si substrates.

Random lasing from dye-doped negative liquid crystals using ZnO nanoparticles as tunable scatters

NASA Astrophysics Data System (ADS)

Li, Long-Wu; Shang, Zhen-Zhen; Deng, Luogen

2016-09-01

This work demonstrates the realization of a lasing in scattering media, which contains dispersive solution of ZnO nanoparticles (NPs) and laser dye 4-dicyanomethylene-2-methyle-6-(p-dimethylaminostyryl)-4H-pyran(DCM) in negative liquid crystals (LCs) that was injected into a cell. The lasing intensity of the dye-doped negative LC laser can be tuned from low to high if the NPs concentration is increased. The tunability of the laser is attributable to the clusters-sensitive feature in effective refractive index of the negative LCs. Such a tunable negative liquid crystal laser can be used in the fabrication of new optical sources, optical communication, and liquid crystal laser displays. Project supported by the Doctoral Science Research Start-up Funding of Guizhou Normal University, China (Grant No. 11904-0514162) and the National Natural Science Foundation of China (Grant No. 11474021).

Characterization of Bivoj/DiPOLE 100: HiLASE 100-J/10-Hz diode pumped solid state laser

NASA Astrophysics Data System (ADS)

Pilar, Jan; De Vido, Mariastefania; Divoky, Martin; Mason, Paul; Hanus, Martin; Ertel, Klaus; Navratil, Petr; Butcher, Thomas; Slezak, Ondrej; Banerjee, Saumyabrata; Phillips, Jonathan; Smith, Jodie; Lucianetti, Antonio; Hernandez-Gomez, Cristina; Edwards, Chris; Collier, John; Mocek, Tomas

2018-02-01

The HiLASE "Bivoj" laser system developed at CLF Rutherford Appleton Laboratory in collaboration with HiLASE team as DiPOLE100 was relocated to Dolni Brezany near Prague, Czechia at the end of 2015 and fully re-commissioned at the end of 2016. In 2016, the system demonstrated average output power of 1kW generating pulses of 105 J at 10 Hz repetition rate for the first time in the world. Since then the system has been subjected to several testing campaigns in order to determine some of its key characteristics. Beam quality, wavefront quality, pointing stability, energy stability and experience with long term operation of 1 kW laser are presented. In addition, depolarization effects have been detected inside the main amplifier. Details on these results along with numerical simulations are presented.

One-year outcomes of AquaLase cataract surgery.

PubMed

Yoo, Sonia H; Bhatt, Anand B

2007-01-01

The authors report surgical experience and clinical outcomes up to 1 year postoperatively in patients who underwent cataract surgery with the AquaLase liquefaction device (Alcon Laboratories, Fort Worth, TX). The device is a handpiece option for use with Alcon's Infiniti Vision System that uses heated balanced saline solution micropulses to liquefy lenticular material. Twenty-seven eyes of 23 patients underwent cataract extraction with the use of the AquaLase liquefaction device. The average age of participants was 68 years, and the average nuclear sclerotic grade was 1.96 on a 4-point scale. Outcomes were judged by metrics such as visual acuity, inflammation, endothelial cell count, and postoperative posterior capsule opacification. At 30 days postoperatively, 78% of eyes had a best-corrected visual acuity of 20/20. Visual acuity was 20/25 or better 1 year postoperatively in 88% of patients without complications except conversion to ultrasound phacoemulsification for two dense cataracts.

Spatial and polarization entanglement of lasing patterns and related dynamic behaviors in laser-diode-pumped solid-state lasers.

PubMed

Otsuka, K; Chu, S-C; Lin, C-C; Tokunaga, K; Ohtomo, T

2009-11-23

To provide the underlying physical mechanism for formations of spatial- and polarization-entangled lasing patterns (namely, SPEPs), we performed experiments using a c-cut Nd:GdVO(4) microchip laser with off-axis laser-diode pumping. This extends recent work on entangled lasing pattern generation from an isotropic laser, where such a pattern was explained only in terms of generalized coherent states (GCSs) formed by mathematical manipulation. Here, we show that polarization-resolved transverse patterns can be well explained by the transverse mode-locking of distinct orthogonal linearly polarized Ince-Gauss (IG) mode pairs rather than GCSs. Dynamic properties of SPEPs were experimentally examined in both free-running and modulated conditions to identify long-term correlations of IG mode pairs over time. The complete chaos synchronization among IG mode pairs subjected to external perturbation is also demonstrated.

Temperature tuning of lasing emission from dye-doped liquid crystal at intermediate twisted phase

NASA Astrophysics Data System (ADS)

Liao, Kuan-Cheng; Lin, Ja-Hon; Jian, Li-Hao; Chen, Yao-Hui; Wu, Jin-Jei

2015-07-01

Temperature tuning of lasing emission from dye-doped cholesteric liquid crystal (CLC) at intermediate twisted phase has been demonstrated in this work. With heavily doping of 42.5% chiral molecules into the nematic liquid crystals, the shifts of photonic bandgap versus temperature is obviously as thermal controlling of the sample below the certain value. By the differential scanning calorimetr measuremet, we demonstrate the phase transition from the CLC to the smectic phase when the temperature is lowered to be about 15°C. Between CLC and smectic phase, the liquid crystal mixtures are operated at intermediate twisted phase that can be used the temperature related refractive mirror. After pump by the Q-switched Nd:YAG laser, the lasing emission from this dye doped LC mixtures has been demonstrated whose emission wavelength can be tuned from 566 to 637 nm with 1.4°C variation.

1887 nm lasing in Tm3+-doped TeO2-BaF2-Y2O3 glass microstructured fibers

NASA Astrophysics Data System (ADS)

Wang, Shunbin; Yao, Chuanfei; Jia, Zhixu; Qin, Guanshi; Qin, Weiping

2017-04-01

In this paper, we demonstrate ∼2 μm lasing in Tm3+-doped fluorotellurite microstructured fibers. The Tm3+-doped fibers are based on TeO2-BaF2-Y2O3 glasses and fabricated by using a rod-in-tube method. Under the pump of a 1570 nm Er3+-doped fiber laser, lasing at 1887 nm is obtained in a ∼42.5 cm long Tm3+-doped fiber with a threshold pump power of 94 mW. As the pump power increases to 780 mW, the obtained maximum unsaturated power reaches up to ∼408 mW with a slop efficiency of ∼58.1%. This result indicates that the Tm3+-doped fluorotellurite fibers are promising gain media for ∼2 μm fiber lasers.

Intrinsic Josephson junction behaviour of the low Tc superconductor (LaSe) 1.14(NbSe 2)

NASA Astrophysics Data System (ADS)

Kačmarčík, J.; Szabó, P.; Samuely, P.; Rodrigo, J. G.; Suderow, H.; Vieira, S.; Lafond, A.; Meerschaut, A.

2008-04-01

Interlayer magnetotransport measurements on the highly anisotropic (LaSe)1.14(NbSe2) superconductor with Tc ∼ 1.2 K have indicated that this layered compound represents a model system of intrinsic Josephson junctions [P. Szabó et al., Phys. Rev. Lett. 86 (2001) 5990]. Scanning tunneling microscopy at room temperature and tunneling spectroscopy measurements at very low temperatures are presented in this work. STM imaging has revealed the presence of two types of surfaces which can be attributed to the appearance of LaSe or NbSe2 layers on the surface. The use of STM tip made of superconducting lead enabled a precise measurement of the temperature dependence of the superconducting energy gap Δ(T) on the NbSe2 layer. Δ(T) obtained from the surface sensitive STS data support the scenario obtained from our previous interlayer - ergo bulk sensitive magnetotransport measurements.

Lateral cavity photonic crystal surface emitting lasers with ultralow threshold and large power

NASA Astrophysics Data System (ADS)

Wang, Yufei; Qu, Hongwei; Zhou, Wenjun; Jiang, Bin; Zhang, Jianxin; Qi, Aiyi; Liu, Lei; Fu, Feiya; Zheng, Wanhua

2012-03-01

The Bragg diffraction condition of surface-emitting lasing action is analyzed and Γ2-1 mode is chosen for lasing. Two types of lateral cavity photonic crystal surface emitting lasers (LC-PCSELs) based on the PhC band edge mode lateral resonance and vertical emission to achieve electrically driven surface emitting laser without distributed Bragg reflectors in the long wavelength optical communication band are designed and fabricated. Deep etching techniques, which rely on the active layer being or not etched through, are adopted to realize the LC-PCSELs on the commercial AlGaInAs/InP multi-quantum-well (MQW) epitaxial wafer. 1553.8 nm with ultralow threshold of 667 A/cm2 and 1575 nm with large power of 1.8 mW surface emitting lasing actions are observed at room temperature, providing potential values for mass production with low cost of electrically driven PCSELs.

Generation of stimulated noncoherent radiation in light-scattering media exhibiting chemical reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Izmailov, I.A.; Kochelap, V.A.; Mel'nikov, L.Y.

1982-05-01

It is proposed that a feedback resulting from scattering be used to achieve lasing in a disperse reactive medium. The example of a simple two-level system shows that under advanced lasing conditions the quantum efficiency of the radiation emission approaches the quantum efficiency of the excitation of the upper level, and the emission spectrum becomes much narrower. Feasibility of chemical pumping of such a laser is estimated on the basis of calculations of heterophase burning of a drop of a fuel in an oxidizing atmosphere. The growth increment of light is calculated and the threshold conditions for the excitation ofmore » lasing are found. Examples are given to illustrate the feasibility of purely chemical pumping of a laser with a nonresonant feedback. It is shown that dense reactive media can be used in such lasers.« less

Neutron-driven gamma-ray laser

DOEpatents

Bowman, Charles D.

1990-01-01

A lasing cylinder emits laser radiation at a gamma-ray wavelength of 0.87 .ANG. when subjected to an intense neutron flux of about 400 eV neutrons. A 250 .ANG. thick layer of Be is provided between two layers of 100 .ANG. thick layer of .sup.57 Co and these layers are supported on a foil substrate. The coated foil is coiled to form the lasing cylinder. Under the neutron flux .sup.57 Co becomes .sup.58 Co by neutron absorption. The .sup.58 Co then decays to .sup.57 Fe by 1.6 MeV proton emission. .sup.57 Fe then transitions by mesne decay to a population inversion for lasing action at 14.4 keV. Recoil from the proton emission separates the .sup.57 Fe from the .sup.57 Co and into the Be, where Mossbauer emission occurs at a gamma-ray wavelength.

Room-temperature lasing in a single nanowire with quantum dots

NASA Astrophysics Data System (ADS)

Tatebayashi, Jun; Kako, Satoshi; Ho, Jinfa; Ota, Yasutomo; Iwamoto, Satoshi; Arakawa, Yasuhiko

2015-08-01

Semiconductor nanowire lasers are promising as ultrasmall, highly efficient coherent light emitters in the fields of nanophotonics, nano-optics and nanobiotechnology. Although there have been several demonstrations of nanowire lasers using homogeneous bulk gain materials or multi-quantum-wells/disks, it is crucial to incorporate lower-dimensional quantum nanostructures into the nanowire to achieve superior device performance in relation to threshold current, differential gain, modulation bandwidth and temperature sensitivity. The quantum dot is a useful and essential nanostructure that can meet these requirements. However, difficulties in forming stacks of quantum dots in a single nanowire hamper the realization of lasing operation. Here, we demonstrate room-temperature lasing of a single nanowire containing 50 quantum dots by properly designing the nanowire cavity and tailoring the emission energy of each dot to enhance the optical gain. Our demonstration paves the way toward ultrasmall lasers with extremely low power consumption for integrated photonic systems.

Excitation enhancement and extraction enhancement with photonic crystals

DOEpatents

Shapira, Ofer; Soljacic, Marin; Zhen, Bo; Chua, Song-Liang; Lee, Jeongwon; Joannopoulos, John

2015-03-03

Disclosed herein is a system for stimulating emission from at least one an emitter, such as a quantum dot or organic molecule, on the surface of a photonic crystal comprising a patterned dielectric substrate. Embodiments of this system include a laser or other source that illuminates the emitter and the photonic crystal, which is characterized by an energy band structure exhibiting a Fano resonance, from a first angle so as to stimulate the emission from the emitter at a second angle. The coupling between the photonic crystal and the emitter may result in spectral and angular enhancement of the emission through excitation and extraction enhancement. These enhancement mechanisms also reduce the emitter's lasing threshold. For instance, these enhancement mechanisms enable lasing of a 100 nm thick layer of diluted organic molecules solution with reduced threshold intensity. This reduction in lasing threshold enables more efficient organic light emitting devices and more sensitive molecular sensing.

Multiwavelength generation in a random distributed feedback fiber laser using an all fiber Lyot filter.

PubMed

Sugavanam, S; Yan, Z; Kamynin, V; Kurkov, A S; Zhang, L; Churkin, D V

2014-02-10

Multiwavelength lasing in the random distributed feedback fiber laser is demonstrated by employing an all fiber Lyot filter. Stable multiwavelength generation is obtained, with each line exhibiting sub-nanometer line-widths. A flat power distribution over multiple lines is obtained, which indicates that the power between lines is redistributed in nonlinear mixing processes. The multiwavelength generation is observed both in first and second Stokes waves.

GRIP Experiment 2010

NASA Image and Video Library

2010-08-15

Syed Ismail, from the Langley Research Center, principal investigator for the Lidar Atmospheric Sensing Experiment (LASE) is seen aboard the NASA DC-8 aircraft, Monday, August 16, 2010, at Fort Lauderdale Hollywood International Airport in Fort Lauderdale, Fla. The Genesis and Rapid Intensification Processes (GRIP) experiment is a NASA Earth science field experiment in 2010 that is being conducted to better understand how tropical storms form and develop into major hurricanes. Photo Credit: (NASA/Paul E. Alers)

Raman lasing in As₂S₃ high-Q whispering gallery mode resonators.

PubMed

Vanier, Francis; Rochette, Martin; Godbout, Nicolas; Peter, Yves-Alain

2013-12-01

We report the first observation of a nonlinear process in a chalcogenide microresonator. Raman scattering and stimulated Raman scattering leading to laser oscillation is observed in microspheres made of As₂S₃. The coupled pump power threshold is as low as 13 μW using a pump wavelength of 1550 nm. The quality factor of the chalcogenide microresonator is also the highest ever reported with Q>7×10(7).

Time Domain Spectral Hole-Burning Storage

DTIC Science & Technology

1994-05-02

unlimited. - ~I& AISTRACT VAtfkAanu 2W, Wors This work achieved wsveral ubsantial reslts. A highly stabilized lase system suiable for many detaild...mlies of data storage phenomena was consructed and made to wor This la was es- sential for the inUetig s which follwed. Using the stabilized lase, a re...time courelaor was dmon ed, which co ly ientd all occumances of a test sequence imbedded in random data. S ) This corxator is the fint de1moration of

Simultaneous RGB lasing from a single-chip polymer device.

PubMed

Yamashita, Kenichi; Takeuchi, Nobutaka; Oe, Kunishige; Yanagi, Hisao

2010-07-15

This Letter describes the fabrication and operation of a single-chip white-laser device. The laser device has a multilayered structure consisting of three laser layers. Each laser layer comprises polymer claddings and a waveguide core doped with organic dye. In each laser layer, grating corrugations were fabricated by UV-nanoimprint lithography that act as distributed-feedback cavity structures. Under optical pumping, lasing output with red, green, and blue colors was simultaneously obtained from the sample edge.

Ultra-low threshold polariton condensation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Steger, Mark; Fluegel, Brian; Alberi, Kirstin

Here, we demonstrate the condensation of microcavity polaritons with a very sharp threshold occurring at a two orders of magnitude pump intensity lower than previous demonstrations of condensation. The long cavity lifetime and trapping and pumping geometries are crucial to the realization of this low threshold. Polariton condensation, or 'polariton lasing' has long been proposed as a promising source of coherent light at a lower threshold than traditional lasing, and these results indicate some considerations for optimizing designs for lower thresholds.

Antiguided fiber ribbon laser

DOEpatents

Wilcox, Russel B [El Cerrito, CA; Page, Ralph H [Castro Valley, CA; Beach, Raymond J [Livermore, CA; Feit, Michael D [Livermore, CA; Payne, Stephen A [Castro Valley, CA

2003-05-27

The invention is a ribbon of an optical material with a plurality of cores that run along its length. The plurality of cores includes lasing impurity doped cores in an alternating spaced arrangement with index-modifying impurity doped cores. The ribbon comprises an index of refraction that is substantially equal to or greater than the indices of refraction of said array of lasing impurity doped cores. Index-increasing impurity doped cores promote antiguiding and leaky modes which provide more robust single "supermode" operation.

High-Speed Stark Wavelength Tuning of MidIR Interband Cascade Lasers

DTIC Science & Technology

2007-03-15

STARK WAVELENGTH TUNING OF MidIR ICLs 361 Fig. 2. Lasing spectra of the tunable ICL at different bias currents. injection region at before tunneling ...the energy separation between and (and hence the emission wavelength) undergoes a linear Stark shift that depends on the bias current which controls...response Fig. 3. Lasing spectra of the tunable ICL at different bias modulation frequen- cies. Fig. 4. Dependence of the intensity of the Line 2 on bias

Ultra-low threshold polariton condensation

DOE PAGES

Steger, Mark; Fluegel, Brian; Alberi, Kirstin; ...

2017-03-13

Here, we demonstrate the condensation of microcavity polaritons with a very sharp threshold occurring at a two orders of magnitude pump intensity lower than previous demonstrations of condensation. The long cavity lifetime and trapping and pumping geometries are crucial to the realization of this low threshold. Polariton condensation, or 'polariton lasing' has long been proposed as a promising source of coherent light at a lower threshold than traditional lasing, and these results indicate some considerations for optimizing designs for lower thresholds.

Green, yellow and bright red (In,Ga,Al)P-GaP diode lasers grown on high-index GaAs substrates

NASA Astrophysics Data System (ADS)

Ledentsov, N. N.; Shchukin, V. A.; Shernyakov, Yu. M.; Kulagina, M. M.; Payusov, A. S.; Gordeev, N. Yu.; Maximov, M. V.; Cherkashin, N. A.

2017-02-01

Low threshold current density (<400 A/cm2) injection lasing in (AlxGa1-x)0.5In0.5P-GaAs-based diodes down to the green spectral range (<570 nm) is obtained. The epitaxial structures are grown on high-index (611)A and (211)A GaAs substrates by metal-organic vapor phase epitaxy and contain tensile-strained GaP-enriched insertions aimed at preventing escape of the injected nonequilibrium electrons from the active region. Extended waveguide concept results in a vertical beam divergence with a full width at half maximum of 15o for (611)A substrates. The lasing at 569 nm is realized at 85 K. In the orange-red laser diode structure low threshold current density (200 A/cm2) in the orange spectral range (598 nm) is realized at 85 K. The latter devices demonstrate room temperature lasing at 628 nm at 2 kA/cm2 and a total power above 3W. The red laser diodes grown on (211)A substrates demonstrate vertically multimode lasing far field pattern indicating a lower optical confinement factor for the fundamental mode as compared to the devices grown on (611)A. However the temperature stability of the threshold current and the wavelength stability are significantly higher for (211)A-grown structures in agreement with the conduction band modeling data.

LASE measurements of aerosols and water vapor during TARFOX

NASA Technical Reports Server (NTRS)

Ferrare, Richard A.; Ismail, Syed; Browell, Edward V.; Brackett, Vincent G.; Kooi, Susan A.; Clayton, Marian B.; Melfi, Harvey; Whiteman, David N.; Schwenner, Geary; Evans, Keith D.;

Metasurface-assisted orbital angular momentum carrying Bessel-Gaussian Laser: proposal and simulation.

PubMed

Zhou, Nan; Wang, Jian

2018-05-23

Bessel-Gaussian beams have distinct properties of suppressed diffraction divergence and self-reconstruction. In this paper, we propose and simulate metasurface-assisted orbital angular momentum (OAM) carrying Bessel-Gaussian laser. The laser can be regarded as a Fabry-Perot cavity formed by one partially transparent output plane mirror and the other metasurface-based reflector mirror. The gain medium of Nd:YVO 4 enables the lasing wavelength at 1064 nm with a 808 nm laser serving as the pump. The sub-wavelength structure of metasurface facilitates flexible spatial light manipulation. The compact metasurface-based reflector provides combined phase functions of an axicon and a spherical mirror. By appropriately selecting the size of output mirror and inserting mode-selection element in the laser cavity, different orders of OAM-carrying Bessel-Gaussian lasing modes are achievable. The lasing Bessel-Gaussian 0 , Bessel-Gaussian 01 + , Bessel-Gaussian 02 + and Bessel-Gaussian 03 + modes have high fidelities of ~0.889, ~0.889, ~0.881 and ~0.879, respectively. The metasurface fabrication tolerance and the dependence of threshold power and output lasing power on the length of gain medium, beam radius of pump and transmittance of output mirror are also discussed. The obtained results show successful implementation of metasurface-assisted OAM-carrying Bessel-Gaussian laser with favorable performance. The metasurface-assisted OAM-carrying Bessel-Gaussian laser may find wide OAM-enabled communication and non-communication applications.

Investigation of Coronal Leakage of Root Fillings after Smear Layer Removal with EDTA or Er,Cr:YSGG Laser through Capillary Flow Porometry

PubMed Central

Vergauwen, Tom Edgard Maria; Michiels, Rafaël; Torbeyns, Dries; Meire, Maarten; De Moor, Roeland Jozef Gentil

2014-01-01

No studies have been performed evaluating the marginal seal of root fillings after direct exposure of root canal (RC) walls to Er,Cr:YSGG laser irradiation. Therefore, 75 root filled teeth (5 × 15–cold lateral condensation) were analyzed for through-and-through leakage (TTL) using capillary flow porometry (CFP). The cleaning protocol determined the experimental groups: (1) irrigation with NaOCl 2.5% and EDTA 17% or standard protocol (SP), (2) SP + Er,Cr:YSGG lasing (dried RC), (3) NaOCl 2.5% + Er,Cr:YSGG lasing (dried RC), (4) SP + Er,Cr:YSGG lasing (wet RC), and (5) NaOCl 2.5% + Er,Cr:YSGG lasing (wet RC). Groups 6 to 10 consisted of the same filled teeth with resected apices. Resection was performed after the first CFP measurement. CFP was used to assess minimum, mean flow, and maximum pore diameters after 48 h. Statistics were performed using nonparametric tests (P > 0.05). Additional three roots per group were submitted to SEM of the RC walls. TTL was observed in all groups without statistically significant differences between the different groups for minimum, mean, and maximum pore diameter (P > 0.05). In this study, the use of EDTA and/or Er,Cr:YSGG laser did not reduce through-and-through leakage in nonresected and resected roots. PMID:24696685

Quasi-continuous frequency tunable terahertz quantum cascade lasers with coupled cavity and integrated photonic lattice.

PubMed

Kundu, Iman; Dean, Paul; Valavanis, Alexander; Chen, Li; Li, Lianhe; Cunningham, John E; Linfield, Edmund H; Davies, A Giles

2017-01-09

We demonstrate quasi-continuous tuning of the emission frequency from coupled cavity terahertz frequency quantum cascade lasers. Such coupled cavity lasers comprise a lasing cavity and a tuning cavity which are optically coupled through a narrow air slit and are operated above and below the lasing threshold current, respectively. The emission frequency of these devices is determined by the Vernier resonance of longitudinal modes in the lasing and the tuning cavities, and can be tuned by applying an index perturbation in the tuning cavity. The spectral coverage of the coupled cavity devices have been increased by reducing the repetition frequency of the Vernier resonance and increasing the ratio of the free spectral ranges of the two cavities. A continuous tuning of the coupled cavity modes has been realized through an index perturbation of the lasing cavity itself by using wide electrical heating pulses at the tuning cavity and exploiting thermal conduction through the monolithic substrate. Single mode emission and discrete frequency tuning over a bandwidth of 100 GHz and a quasi-continuous frequency coverage of 7 GHz at 2.25 THz is demonstrated. An improvement in the side mode suppression and a continuous spectral coverage of 3 GHz is achieved without any degradation of output power by integrating a π-phase shifted photonic lattice in the laser cavity.

Influence of quantum well inhomogeneities on absorption, spontaneous emission, photoluminescence decay time, and lasing in polar InGaN quantum wells emitting in the blue-green spectral region

NASA Astrophysics Data System (ADS)

Gladysiewicz, M.; Kudrawiec, R.; Syperek, M.; Misiewicz, J.; Siekacz, M.; Cywinski, G.; Khachapuridze, A.; Suski, T.; Skierbiszewski, C.

2014-06-01

It is shown that in polar InGaN QWs emitting in the blue-green spectral region a Stokes shift between spontaneous emission (SE) and optical transition observed in contactless electroreflectance (CER) spectrum (absorption-like technique) can be observed even at room temperature, despite the fact that the SE is not associated with localized states. Time resolved photoluminescence measurements clearly confirm that the SE is strongly localized at low temperatures whereas at room temperature the carrier localization disappears and the SE can be attributed to the fundamental transition in this QW. The Stokes shift is observed in this QW system because of the large built-in electric field, i.e., the CER transition is a superposition of all optical transitions with non-zero electron-hole overlap integrals and, therefore, the energy of this transition does not correspond to the fundamental transition of InGaN QW. Lasing from this QW has been observed at the wavelength of 475 nm, whereas the SE was observed at 500 nm. The 25 nm shift between the lasing and SE is observed because of a screening of the built-in electric field by photogenerated carriers. However, our analysis shows that the built-in electric field inside the InGaN QW region is not fully screened under the lasing conditions.

Nonlinear optical properties, upconversion and lasing in metal-organic frameworks.

PubMed

Medishetty, Raghavender; Zaręba, Jan K; Mayer, David; Samoć, Marek; Fischer, Roland A

2017-08-14

The building block modular approach that lies behind coordination polymers (CPs) and metal-organic frameworks (MOFs) results not only in a plethora of materials that can be obtained but also in a vast array of material properties that could be aimed at. Optical properties appear to be particularly predetermined by the character of individual structural units and by the intricate interplay between them. Indeed, the "design principles" shaping the optical properties of these materials seem to be well explored for luminescence and second-harmonic generation (SHG) phenomena; these have been covered in numerous previous reviews. Herein, we shine light on CPs and MOFs as optical media for state-of-the-art photonic phenomena such as multi-photon absorption, triplet-triplet annihilation (TTA) and stimulated emission. In the first part of this review we focus on the nonlinear optical (NLO) properties of CPs and MOFs, with a closer look at the two-photon absorption property. We discuss the scope of applicability of most commonly used measurement techniques (Z-scan and two-photon excited fluorescence (TPEF)) that can be applied for proper determination of the NLO properties of these materials; in particular, we suggest recommendations for their use, along with a discussion of the best reporting practices of NLO parameters. We also outline design principles, employing both intramolecular and intermolecular strategies, that are necessary for maximizing the NLO response. A review of recent literature on two-, three- and multi-photon absorption in CPs and MOFs is further supplemented with application-oriented processes such as two-photon 3D patterning and data storage. Additionally, we provide an overview of the latest achievements in the field of frequency doubling (SHG) and tripling (third-harmonic generation, THG) in these materials. Apart from nonlinear processes, in the next sections we also target the photonic properties of MOFs that benefit from their porosity, and resulting from this their ability to serve as containers for optically-active molecules. Thus, we survey dye@MOF composites as novel media in which efficient upconversion via triplet energy migration (TEM) occurs as well as materials for stimulated emission and multi-photon pumped lasing. Prospects for producing lasing as an intrinsic property of MOFs has also been discussed. Overall, further development of the optical processes highlighted herein should allow for realization of various photonic, data storage, biomedical and optoelectronic applications.

Mesoscopic coherence in light scattering from cold, optically dense and disordered atomic systems

NASA Astrophysics Data System (ADS)

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

2017-02-01

Coherent effects manifested in light scattering from cold, optically dense and disordered atomic systems are reviewed from a primarily theoretical point of view. Development of the basic theoretical tools is then elaborated through several physical atomic physics based processes which have been at least partly explored experimentally. These include illustrations drawn from the coherent backscattering effect, random lasing in atomic gases, quantum memories and light-atoms interface assisted by the light trapping mechanism. Current understanding and challenges associated with the transition to high atomic densities and cooperativity in the scattering process are also discussed in some detail.

Solid-state-based analog of optomechanics

DOE PAGES

Naumann, Nicolas L.; Droenner, Leon; Carmele, Alexander; ...

2016-09-01

In this study, we investigate a semiconductor quantum dot as a microscopic analog of a basic optomechanical setup. We show that optomechanical features can be reproduced by the solid-state platform, arising from parallels of the underlying interaction processes, which in the optomechanical case is the radiation pressure coupling and in the semiconductor case the electron–phonon coupling. We discuss bistabilities, lasing, and phonon damping, and recover the same qualitative behaviors for the semiconductor and the optomechanical cases expected for low driving strengths. However, in contrast to the optomechanical case, distinct signatures of higher order processes arise in the semiconductor model.

Kinetic model of stimulated emission created by resonance pumping of aluminum laser-induced plasma

NASA Astrophysics Data System (ADS)

Gornushkin, I. B.; Kazakov, A. Ya.

2017-06-01

Stimulated emission observed experimentally in an aluminum laser induced plasma is modeled via a kinetic approach. The simulated emission at several cascade transitions is created by a pump laser guided through the plasma at several microseconds after its creation and tuned in resonance with the strong 3s23p-3s24s transition at 266 nm. A two-dimensional space-time collisional radiative plasma model explains the creation of the population inversion and lasing at wavelengths of 2100 n m and 396.1 nm. The population inversion for lasing at 2100 n m is created by depopulation of the ground 3s23p state and population of the 3s25s state via the absorption of the resonant radiation at 266 nm. The population inversion for lasing at 396.1 nm occurs during the laser pulse via the decay of the population of the pumped 3s25s state to the excited 3s24s state via cascade transitions driven optically and by collisions. In particular, efficient are the mixing transitions between neighboring states separated by small gaps on the order of k T at plasma temperatures of 5000-10 000 K. The model predicts that the population inversion and corresponding gain may reach high values even at very moderate pump energy of several μJ per pulse. The efficiency of lasing at 2100 n m and 396.1 nm is estimated to be ˜3% and 0.05%, correspondingly with respect to the pump laser intensity. The gain for lasing at 396.1 nm can reach as high as ˜40 cm-1. The polarization effect that the pump radiation at 266 nm imposes on the stimulated emission at 396.1 nm is discussed. The calculated results are favorably compared to experimental data.

Electrically-pumped compact hybrid silicon microring lasers for optical interconnects.

PubMed

Liang, Di; Fiorentino, Marco; Okumura, Tadashi; Chang, Hsu-Hao; Spencer, Daryl T; Kuo, Ying-Hao; Fang, Alexander W; Dai, Daoxin; Beausoleil, Raymond G; Bowers, John E

2009-10-26

We demonstrate an electrically-pumped hybrid silicon microring laser fabricated by a self-aligned process. The compact structure (D = 50 microm) and small electrical and optical losses result in lasing threshold as low as 5.4 mA and up to 65 degrees C operation temperature in continuous-wave (cw) mode. The spectrum is single mode with large extinction ratio and small linewidth observed. Application as on-chip optical interconnects is discussed from a system perspective.

Gold Coating

NASA Technical Reports Server (NTRS)

1997-01-01

Epner Technology Inc. responded to a need from Goddard Space Flight Center for the ultimate in electroplated reflectivity needed for the Mars Global Surveyor Mars Orbiter Laser Altimeter (MOLA). Made of beryllium, the MOLA mirror was coated by Epner Technology Laser Gold process, specially improved for the project. Improved Laser Gold- coated reflectors have found use in an epitaxial reactor built for a large semiconductor manufacturer as well as the waveguide in Braun-Thermoscan tympanic thermometer and lasing cavities in various surgical instruments.

Resonantly photo-pumped nickel-like erbium X-ray laser

DOEpatents

Nilsen, Joseph

1990-01-01

A resonantly photo-pumped X-ray laser (10) that enhances the gain of seve laser lines that also lase because of collisional excitations and recombination processes, is described. The laser comprises an aluminum (12) and erbium (14) foil combination (16) that is driven by two beams (18, 20) of intense line focused (22, 24) optical laser radiation. Ground state nickel-like erbium ions (34) are resonantly photo-pumped by line emission from hydrogen-like aluminum ions (32).

Electron beam method and apparatus for obtaining uniform discharges in electrically pumped gas lasers

DOEpatents

Fenstermacher, Charles A.; Boyer, Keith

1986-01-01

A method and apparatus for obtaining uniform, high-energy, large-volume electrical discharges in the lasing medium of a gas laser whereby a high-energy electron beam is used as an external ionization source to ionize substantially the entire volume of the lasing medium which is then readily pumped by means of an applied potential less than the breakdown voltage of the medium. The method and apparatus are particularly useful in CO.sub.2 laser systems.

Enhancement of short-pulse recombination-pumped gain by soft-x-ray photoionization of the ground state

NASA Astrophysics Data System (ADS)

Apruzese, J. P.; Umstadter, D.

1996-02-01

The gain achieved in lasing to the ground state following short-pulse field ionization by a pump laser is highly transient. It will usually persist for only tens of picoseconds because of the rapid filling and negligible emptying of the ground state. Employing a detailed atomic model of lasing in hydrogen, we show that the removal of ground-state population by an appropriate broadband ionizing radiation field can enhance and prolong the gain in such a laser.

Modulation doping of quantum dot laser active area and its impact on lasing performance

NASA Astrophysics Data System (ADS)

Konoplev, S. S.; Savelyev, A. V.; Korenev, V. V.; Maximov, M. V.; Zhukov, A. E.

2015-11-01

We present a theoretical study of modulation doping of active region in the quantum dot (QD) laser and corresponding issues of QD charge neutrality violation, a band diagram of the laser and charge carriers distribution in the structure. Modulation doping is discussed as a possible technique to control laser output characteristics. It was shown that modulation doping leads to an increase of threshold current of lasing through excited QD optical transition together with power emission from QD ground state.

HiLASE Project: high intensity lasers for industrial and scientific applications

NASA Astrophysics Data System (ADS)

Rostohar, Danijela; Lucianetti, Antonio; Endo, Akira; Mocek, Tomas

2015-01-01

The Czech national R&D project HiLASE is a platform for development of advance high repetition rate, diode pump solid state lasers (DPSSL) systems with energies in the range from mJ to 10J and repetition rate from 10 Hz to 100 kHz. In this paper an overview and a status of the project will be given. Additionally some applications of these lasers in the hi-tech industry, which initiated their development, will be also presented.

Efficient lasing in Yb:(YLa){sub 2}O{sub 3} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Snetkov, I L; Mukhin, I B; Palashov, O V

2015-02-28

A high-optical-quality sample of Yb{sub 0.1}Y{sub 1.7}La{sub 0.2}O{sub 3} ceramics is prepared using a recently developed technique of selfpropagating high-temperature synthesis of rare-earth-doped yttrium oxide nanopowder from acetate – nitrates of metals. Its optical and spectral characteristics are studied, and quasi-cw lasing at a wavelength of 1033 nm is achieved with a power of 7 W and a slope efficiency of 25%. (lasers)

Experimental Investigation and Computer Modeling of Optical Switching in Distributed Bragg Reflector and Vertical Cavity Surface Emitting Laser Structures.

DTIC Science & Technology

1995-12-01

of a Molecular Beam Epitaxy (MBE) system prior to growing a Vertical Cavity Surface Emitting Laser ( VCSEL ). VCSEL bistability is discussed later in...addition, optical bistability 1 in the reflectivity of a DBR, as well as in the lasing power, wavelength, and beam divergence of a lasing VCSEL are...Spectral Reflectivity of AlGaAs/AlAs VCSEL Top DBR Mirror Cavity Bottom DBR Mirror Substrate Output Beam Resonance Pump Minimum Stop Band Figure 2. VCSEL

Room-temperature lasing operation of a quantum-dot vertical-cavity surface-emitting laser

NASA Astrophysics Data System (ADS)

Saito, Hideaki; Nishi, Kenichi; Ogura, Ichiro; Sugou, Shigeo; Sugimoto, Yoshimasa

1996-11-01

Self-assembled growth of quantum dots by molecular-beam epitaxy is used to form the active region of a vertical-cavity surface-emitting laser (VCSEL). Ten layers of InGaAs quantum dots are stacked in order to increase the gain. This quantum-dot VCSEL has a continuous-wave operating current of 32 mA at room temperature. Emission spectra at various current injections demonstrate that the lasing action is associated with a higher-order transition in the quantum dots.

Excitonic lasing of strain-free InP(As) quantum dots in AlInAs microdisk

NASA Astrophysics Data System (ADS)

Lebedev, D. V.; Kulagina, M. M.; Troshkov, S. I.; Vlasov, A. S.; Davydov, V. Y.; Smirnov, A. N.; Bogdanov, A. A.; Merz, J. L.; Kapaldo, J.; Gocalinska, A.; Juska, G.; Moroni, S. T.; Pelucchi, E.; Barettin, D.; Rouvimov, S.; Mintairov, A. M.

2017-03-01

Formation, emission, and lasing properties of strain-free InP(As)/AlInAs quantum dots (QDs) embedded in AlInAs microdisk (MD) cavity were investigated using transmission electron microscopy and photoluminescence (PL) techniques. In MD structures, the QDs have the nano-pan-cake shape with the height of ˜2 nm, the lateral size of 20-50 nm, and the density of ˜5 × 109 cm-2. Their emission observed at ˜940 nm revealed strong temperature quenching, which points to exciton decomposition. It also showed unexpected type-I character, indicating In-As intermixing as confirmed by band structure calculations. We observed lasing of InP(As) QD excitons into whispering gallery modes in MD having the diameter of ˜3.2 μm and providing a free spectral range of ˜27 nm and quality factors up to Q˜13 000. Threshold of ˜50 W/cm2 and spontaneous emission coupling coefficient of ˜0.2 were measured for this MD-QD system.

Single mode wavelength control of modulated AlGaAs lasers with external and internal etalon feedback

NASA Technical Reports Server (NTRS)

Maynard, William L.

1989-01-01

Single mode lasing without mode hops has been obtained for VSIS and CSP laser diodes with an external etalon attached to the laser's front facet for up to an 8 C range CW and a 4 C range pulsed, with .07 nm/C tuning. Tests of thin tapered-thickness (TTT) laser diodes show CW and pulsed single mode lasing over 10 C and 2 C ranges, respectively, with .08 nm/C tuning. An analysis of the TTT structure reveals the equivalent of an internal etalon. The time-resolved pulsed behavior for both types of lasers show single mode lasing within the proper temperature ranges with minor modes present only early in the optical pulse, if at all. The external etalon produces noticeable interference fringes in the farfield pattern, while those of the TTT lasers are smooth. Ongoing CW lifetest results indicate stability to within one longitudinal mode after a few hundred hours of operation, along with at least several thousand hours lifetime.

Supercontinuum generation and lasing in thulium doped tellurite microstructured fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jia, Zhi-Xu; Liu, Lai; Yao, Chuan-Fei

2014-02-14

We report supercontinuum (SC) generation in Tm{sup 3+} doped tellurite microstructured fibers (TMFs) pumped by a 1.56 μm femtosecond fiber laser. In comparison with SC generation in undoped TMFs, the SC spectral bandwidth and the spectral intensity in the wavelength region of >1.9 μm are evidently enlarged in Tm{sup 3+} doped TMFs owing to the contribution of the combination of linear gain of Tm{sup 3+} and the nonlinear optical effects to spectral broadening. Furthermore, a transition from SC generation to 1.887 μm lasing (Tm{sup 3+}: {sup 3}F{sub 4}→{sup 3}H{sub 6} transition) is observed in Tm{sup 3+} doped TMFs by varying the pulse widthmore » of the pump laser from 0.29 to 3.47 ps, which gives the evidence of the above spectral broadening mechanism. This is the first observation of the transition from SC generation to lasing, to the best of our knowledge.« less

Controlling Disorder by Electric Field Directed Reconfiguration of Nanowires to Tune Random Lasing.

PubMed

Donahue, Philip P; Zhang, Chenji; Nye, Nicholas; Miller, Jennifer; Wang, Cheng-Yu; Tang, Rong; Christodoulides, Demetrios; Keating, Christine D; Liu, Zhiwen

2018-06-27

Top-down fabrication is commonly used to provide positioning control of optical structures; yet, it places stringent limitations on component materials and oftentimes, dynamic reconfigurability is challenging to realize. Here we present a reconfigurable nanoparticle platform that can integrate heterogeneous particle assembly of different shapes, sizes, and material compositions. We demonstrate dynamic manipulation of disorder in this platform and use it to controllably enhance or frustrate random laser emission for a suspension of titanium dioxide nanowires in a dye solution. Using an alternating current electric field, we control the nanowire orientation to dynamically control the collective scattering of the sample and thus light confinement. Our theoretical model indicates that an increase of 22% in scattering coefficient can be achieved for the experimentally determined nanowire length distribution upon alignment. As a result, a nearly 20-fold enhancement in lasing intensity was achieved. We illustrate the generality of the approach by demonstrating enhanced lasing for aligned nanowires of other materials including gold, mixed gold/dielectric and vanadium oxide (VxOy).

Reduction of parasitic lasing

NASA Technical Reports Server (NTRS)

Storm, Mark E. (Inventor)

1994-01-01

A technique was developed which carefully retro-reflects precisely controlled amounts of light back into a laser system thereby intentionally forcing the laser system components to oscillate in a new resonator called the parasitic oscillator. The parasitic oscillator uses the laser system to provide the gain and an external mirror is used to provide the output coupling of the new resonator. Any change of gain or loss inside the new resonator will directly change the lasing threshold of the parasitic oscillator. This change in threshold can be experimentally measured as a change in the absolute value of reflectivity, provided by the external mirror, necessary to achieve lasing in the parasitic oscillator. Discrepancies between experimental data and a parasitic oscillator model are direct evidence of optical misalignment or component performance problems. Any changes in the optical system can instantly be measured as a change in threshold for the parasitic oscillator. This technique also enables aligning the system for maximum parasitic suppression with the system fully operational.

Toward continuous-wave operation of organic semiconductor lasers

PubMed Central

Sandanayaka, Atula S. D.; Matsushima, Toshinori; Bencheikh, Fatima; Yoshida, Kou; Inoue, Munetomo; Fujihara, Takashi; Goushi, Kenichi; Ribierre, Jean-Charles; Adachi, Chihaya

2017-01-01

The demonstration of continuous-wave lasing from organic semiconductor films is highly desirable for practical applications in the areas of spectroscopy, data communication, and sensing, but it still remains a challenging objective. We report low-threshold surface-emitting organic distributed feedback lasers operating in the quasi–continuous-wave regime at 80 MHz as well as under long-pulse photoexcitation of 30 ms. This outstanding performance was achieved using an organic semiconductor thin film with high optical gain, high photoluminescence quantum yield, and no triplet absorption losses at the lasing wavelength combined with a mixed-order distributed feedback grating to achieve a low lasing threshold. A simple encapsulation technique greatly reduced the laser-induced thermal degradation and suppressed the ablation of the gain medium otherwise taking place under intense continuous-wave photoexcitation. Overall, this study provides evidence that the development of a continuous-wave organic semiconductor laser technology is possible via the engineering of the gain medium and the device architecture. PMID:28508042

An integrated parity-time symmetric wavelength-tunable single-mode microring laser

PubMed Central

Liu, Weilin; Li, Ming; Guzzon, Robert S.; Norberg, Erik J.; Parker, John S.; Lu, Mingzhi; Coldren, Larry A.; Yao, Jianping

2017-01-01

Mode control in a laser cavity is critical for a stable single-mode operation of a ring laser. In this study we propose and experimentally demonstrate an electrically pumped parity-time (PT)-symmetric microring laser with precise mode control, to achieve wavelength-tunable single-mode lasing with an improved mode suppression ratio. The proposed PT-symmetric laser is implemented based on a photonic integrated circuit consisting of two mutually coupled active microring resonators. By incorporating multiple semiconductor optical amplifiers in the microring resonators, the PT-symmetry condition can be achieved by a precise manipulation of the interplay between the gain and loss in the two microring resonators, and the incorporation of phase modulators in the microring resonators enables continuous wavelength tuning. Single-mode lasing at 1,554.148 nm with a sidemode suppression ratio exceeding 36 dB is demonstrated and the lasing wavelength is continuously tunable from 1,553.800 to 1,554.020 nm. PMID:28497784

Analysis of Raman lasing without inversion

NASA Astrophysics Data System (ADS)

Sheldon, Paul Martin

1999-12-01

Properties of lasing without inversion were studied analytically and numerically using Maple computer assisted algebra software. Gain for probe electromagnetic field without population inversion in detuned three level atomic schemes has been found. Matter density matrix dynamics and coherence is explored using Pauli matrices in 2-level systems and Gell-Mann matrices in 3-level systems. It is shown that extreme inversion produces no coherence and hence no lasing. Unitary transformation from the strict field-matter Hamiltonian to an effective two-photon Raman Hamiltonian for multilevel systems has been derived. Feynman diagrams inherent in the derivation show interesting physics. An additional picture change was achieved and showed cw gain possible. Properties of a Raman-like laser based on injection of 3- level coherently driven Λ-type atoms whose Hamiltonian contains the Raman Hamiltonian and microwave coupling the two bottom states have been studied in the limits of small and big photon numbers in the drive field. Another picture change removed the microwave coupler to all orders and simplified analysis. New possibilities of inversionless generation were found.

Solid state laser

NASA Technical Reports Server (NTRS)

Rines, Glen A. (Inventor); Moulton, Peter F. (Inventor); Harrison, James (Inventor)

1993-01-01

A wavelength-tunable, injection-seeded, dispersion-compensated, dispersively-pumped solid state laser includes a lasing medium; a highly reflective mirror; an output coupler; at least one isosceles Brewster prism oriented to the minimum deviation angle between the medium and the mirror for directing light of different wavelengths along different paths; means for varying the angle of the highly reflective mirror relative to the light from at least one Brewster angle for selecting a predetermined laser operating wavelength; a dispersion compensation apparatus associated with the lasing medium; a laser injection seeding port disposed between the dispersion compensation apparatus and one of the mirror and coupler and including a reflective surface at an acute non-Brewster angle to the laser beam for introducing a seed input; a dispersion compensation apparatus associated with the laser medium including opposite chirality optical elements; the lasing medium including a pump surface disposed at an acute angle to the laser beam to define a discrete path for the pumping laser beam separate from the pumped laser beam.

Analysis of corneal endothelial cell density and morphology after laser in situ keratomileusis using two types of femtosecond lasers

PubMed Central

Tomita, Minoru; Waring, George O; Watabe, Miyuki

2012-01-01

Purpose To compare two different femtosecond lasers used for flap creation during laser-assisted in situ keratomileusis (LASIK) surgery in terms of their effects on the corneal endothelium. Methods We performed LASIK surgery on 254 eyes of 131 patients using IntraLase FS60 (Abbott Medical Optics, Inc, Irvine, CA; IntraLase group) and 254 eyes of 136 patients using Femto LDV (Ziemer Group AG, Port, Switzerland; LDV group) for corneal flap creation. The mean cell density, coefficient of variation, and hexagonality of the corneal endothelial cells were determined and the results were statistically compared. Results There were no statistically significant differences in the corneal morphology between pre and post LASIK results in each group, nor were there significant differences between the results of both groups at 3 months post LASIK. Conclusions Both IntraLase FS60 and Ziemer Femto LDV are able to create flaps without significant adverse effects on the corneal endothelial morphology through 3 months after LASIK surgery. PMID:23055680

Lasing characteristics of refractive-index-matched composite Y3Al5O12 rods employing transparent ceramics for solar-pumped lasers

NASA Astrophysics Data System (ADS)

Hasegawa, Kazuo; Ichikawa, Tadashi; Takeda, Yasuhiko; Ikesue, Akio; Ito, Hiroshi; Motohiro, Tomoyoshi

2018-04-01

We have proposed a new configuration of solar-pumped lasers employing transparent ceramic rods. The laser rod has a composite structure consisting of a Nd/Cr:YAG gain domain surrounded by Gd:YAG with the same refractive index as that of Nd/Cr:YAG. The lasing mode is well controlled by the output coupler, and the parasitic oscillation is suppressed, owing to the refractive index matching. A high laser slope efficiency and a low laser oscillation threshold were achieved owing to the suppressed absorption outside the lasing mode, which was previously a serious issue for the end-pumping configuration using a high-NA focusing optics. The laser oscillation threshold of 136 mW and the slope efficiency of 25.3% were derived. Thus, we have resolved the issue of useless absorption associated with the high-NA end-pumping, and achieved significant improvements compared with the conventional structure of uniform Nd/Cr:YAG.

An integrated parity-time symmetric wavelength-tunable single-mode microring laser.

PubMed

Liu, Weilin; Li, Ming; Guzzon, Robert S; Norberg, Erik J; Parker, John S; Lu, Mingzhi; Coldren, Larry A; Yao, Jianping

2017-05-12

Mode control in a laser cavity is critical for a stable single-mode operation of a ring laser. In this study we propose and experimentally demonstrate an electrically pumped parity-time (PT)-symmetric microring laser with precise mode control, to achieve wavelength-tunable single-mode lasing with an improved mode suppression ratio. The proposed PT-symmetric laser is implemented based on a photonic integrated circuit consisting of two mutually coupled active microring resonators. By incorporating multiple semiconductor optical amplifiers in the microring resonators, the PT-symmetry condition can be achieved by a precise manipulation of the interplay between the gain and loss in the two microring resonators, and the incorporation of phase modulators in the microring resonators enables continuous wavelength tuning. Single-mode lasing at 1,554.148 nm with a sidemode suppression ratio exceeding 36 dB is demonstrated and the lasing wavelength is continuously tunable from 1,553.800 to 1,554.020 nm.

Terahertz light-emitting graphene-channel transistor toward single-mode lasing

NASA Astrophysics Data System (ADS)

Yadav, Deepika; Tamamushi, Gen; Watanabe, Takayuki; Mitsushio, Junki; Tobah, Youssef; Sugawara, Kenta; Dubinov, Alexander A.; Satou, Akira; Ryzhii, Maxim; Ryzhii, Victor; Otsuji, Taiichi

2018-03-01

A distributed feedback dual-gate graphene-channel field-effect transistor (DFB-DG-GFET) was fabricated as a current-injection terahertz (THz) light-emitting laser transistor. We observed a broadband emission in a 1-7.6-THz range with a maximum radiation power of 10 μW as well as a single-mode emission at 5.2 THz with a radiation power of 0.1 μW both at 100 K when the carrier injection stays between the lower cutoff and upper cutoff threshold levels. The device also exhibited peculiar nonlinear threshold-like behavior with respect to the current-injection level. The LED-like broadband emission is interpreted as an amplified spontaneous THz emission being transcended to a single-mode lasing. Design constraints on waveguide structures for better THz photon field confinement with higher gain overlapping as well as DFB cavity structures with higher Q factors are also addressed towards intense, single-mode continuous wave THz lasing at room temperature.

Toward continuous-wave operation of organic semiconductor lasers.

PubMed

Sandanayaka, Atula S D; Matsushima, Toshinori; Bencheikh, Fatima; Yoshida, Kou; Inoue, Munetomo; Fujihara, Takashi; Goushi, Kenichi; Ribierre, Jean-Charles; Adachi, Chihaya

2017-04-01

The demonstration of continuous-wave lasing from organic semiconductor films is highly desirable for practical applications in the areas of spectroscopy, data communication, and sensing, but it still remains a challenging objective. We report low-threshold surface-emitting organic distributed feedback lasers operating in the quasi-continuous-wave regime at 80 MHz as well as under long-pulse photoexcitation of 30 ms. This outstanding performance was achieved using an organic semiconductor thin film with high optical gain, high photoluminescence quantum yield, and no triplet absorption losses at the lasing wavelength combined with a mixed-order distributed feedback grating to achieve a low lasing threshold. A simple encapsulation technique greatly reduced the laser-induced thermal degradation and suppressed the ablation of the gain medium otherwise taking place under intense continuous-wave photoexcitation. Overall, this study provides evidence that the development of a continuous-wave organic semiconductor laser technology is possible via the engineering of the gain medium and the device architecture.

Physically transient photonics: random versus distributed feedback lasing based on nanoimprinted DNA.

PubMed

Camposeo, Andrea; Del Carro, Pompilio; Persano, Luana; Cyprych, Konrad; Szukalski, Adam; Sznitko, Lech; Mysliwiec, Jaroslaw; Pisignano, Dario

2014-10-28

Room-temperature nanoimprinted, DNA-based distributed feedback (DFB) laser operation at 605 nm is reported. The laser is made of a pure DNA host matrix doped with gain dyes. At high excitation densities, the emission of the untextured dye-doped DNA films is characterized by a broad emission peak with an overall line width of 12 nm and superimposed narrow peaks, characteristic of random lasing. Moreover, direct patterning of the DNA films is demonstrated with a resolution down to 100 nm, enabling the realization of both surface-emitting and edge-emitting DFB lasers with a typical line width of <0.3 nm. The resulting emission is polarized, with a ratio between the TE- and TM-polarized intensities exceeding 30. In addition, the nanopatterned devices dissolve in water within less than 2 min. These results demonstrate the possibility of realizing various physically transient nanophotonics and laser architectures, including random lasing and nanoimprinted devices, based on natural biopolymers.

Factors influencing flap and INTACS decentration after femtosecond laser application in normal and keratoconic eyes.

PubMed

Ertan, Aylin; Karacal, Humeyra

2008-10-01

To compare accuracy of LASIK flap and INTACS centration following femtosecond laser application in normal and keratoconic eyes. This is a retrospective case series comprising 133 eyes of 128 patients referred for refractive surgery. All eyes were divided into two groups according to preoperative diagnosis: group 1 (LASIK group) comprised 74 normal eyes of 72 patients undergoing LASIK with a femtosecond laser (IntraLase), and group 2 (INTACS group) consisted of 59 eyes of 39 patients with keratoconus for whom INTACS were implanted using a femtosecond laser (IntraLase). Decentration of the LASIK flap and INTACS was analyzed using Pentacam. Temporal decentration was 612.56 +/- 384.24 microm (range: 30 to 2120 microm) in the LASIK group and 788.33 +/- 500.34 microm (range: 30 to 2450 microm) in the INTACS group. A statistically significant difference was noted between the groups in terms of decentration (P < .05). Regression analysis showed that the amount of decentration of the LASIK flap and INTACS correlated with the central corneal thickness in the LASIK group and preoperative sphere and cylinder in the INTACS group, respectively. Decentration with the IntraLase occurred in most cases, especially in keratoconic eyes. The applanation performed for centralization during IntraLase application may flatten and shift the pupil center, and thus cause decentralization of the LASIK flap and INTACS. Central corneal thickness in the LASIK group and preoperative sphere and cylinder in the INTACS group proved to be statistically significant parameters associated with decentration.

(In,Ga,Al)P-GaP laser diodes grown on high-index GaAs surfaces emitting in the green, yellow and bright red spectral range

NASA Astrophysics Data System (ADS)

Ledentsov, N. N.; Shchukin, V. A.; Shernyakov, Yu M.; Kulagina, M. M.; Payusov, A. S.; Gordeev, N. Yu; Maximov, M. V.; Cherkashin, N. A.

2017-02-01

We report on low threshold current density (<400 A cm-2) injection lasing in (Al x Ga1-x )0.5In0.5P-GaAs-based diodes down to the green spectral range (<570 nm). The epitaxial structures are grown on high-index (611)A and (211)A GaAs substrates by metal-organic vapor phase epitaxy and contain tensile-strained GaP-enriched insertions aimed at reflection of the injected nonequilibrium electrons preventing their escape from the active region. Extended waveguide concept results in a vertical beam divergence with a full width at half maximum of 15° for (611)A substrates. The lasing at the wavelength of 569 nm is realized at 85 K. In an orange-red laser diode structure low threshold current density (190 A cm-2) in the orange spectral range (598 nm) is realized at 85 K. The latter devices demonstrated room temperature lasing at 628 nm at ˜2 kA cm-2 and a total power above 3 W. The red laser diodes grown on (211)A substrates demonstrated a far field characteristic for vertically multimode lasing indicating a lower optical confinement factor for the fundamental mode as compared to the devices grown on (611)A. However, as expected from previous research, the temperature stability of the threshold current and the wavelength stability were significantly higher for (211)A-grown structures.

In vitro comparison of debonding force and intrapulpal temperature changes during ceramic orthodontic bracket removal using a carbon dioxide laser.

PubMed

Ma, T; Marangoni, R D; Flint, W

1997-02-01

The aim of this study was to develop a method to reduce the fracture of ceramic orthodontics brackets during debonding procedures. Lasers have been used to thermally soften the bonding resin, which reduces the tensile debonding force. Thermal effects of lasers may create adverse effects to the dental pulp. Previous studies have shown that no pulpal injury occurs when the maximum intrapulpal temperature rise stayed below 2 degrees C. This study investigated the effect of lasing time on intrapulpal temperature increase and tensile debonding force with a 18 watt carbon dioxide laser. Ceramic brackets were bonded to mandibular deciduous bovine teeth and human mandibular first premolars with a photoactivated bonding resin. Modified debonding pliers was used to accurately position the laser beam onto the ceramic bracket. Lasing time required to keep the maximum intrapulpal temperature rise below 2 degrees C was determined by the use of thermocouples inserted into the pulp chambers of the specimens. A tensile debonding force was applied on the control group without lasing and the experimental group was debonded after applying a predetermined lasing time with a carbon dioxide laser. It was found that there was a significance difference (P < 0.05) in tensile debonding force between the control group and the experimental group. It is feasible to use a laser for the debonding of ceramic brackets while keeping the intrapulpal temperature rise below the threshold of pulpal damage.

The Implementation of a Plant and Minor Property Accounting System for the Naval Postgraduate School.

DTIC Science & Technology

1987-09-01

Autmatic Data Processing iquipment CPU Central Procesing Unit DSA Date lase Administrator USU Data "aso Management system D&XC Defense Automation...ground? -How big is a certain piece of plant property (e.g., for shipment)? 2. Nxnected Data Base Volume The current inventory of NPS plant property...System, Automated Data TU I. 89aom so fg o - e In October 136 the aval Postgraduate School was directed to centralize the accounting and control of

Plasma Heating and Ultrafast Semiconductor Laser Modulation Through a Terahertz Heating Field

NASA Technical Reports Server (NTRS)

Li, Jian-Zhong; Ning, C. Z.

2000-01-01

Electron-hole plasma heating and ultrafast modulation in a semiconductor laser under a terahertz electrical field are investigated using a set of hydrodynamic equations derived from the semiconductor Bloch equations. The self-consistent treatment of lasing and heating processes leads to the prediction of a strong saturation and degradation of modulation depth even at moderate terahertz field intensity. This saturation places a severe limit to bandwidth achievable with such scheme in ultrafast modulation. Strategies for increasing modulation depth are discussed.

A Kinetics Model for KrF Laser Amplifiers

NASA Astrophysics Data System (ADS)

Giuliani, J. L.; Kepple, P.; Lehmberg, R.; Obenschain, S. P.; Petrov, G.

1999-11-01

A computer kinetics code has been developed to model the temporal and spatial behavior of an e-beam pumped KrF laser amplifier. The deposition of the primary beam electrons is assumed to be spatially uniform and the energy distribution function of the nascent electron population is calculated to be near Maxwellian below 10 eV. For an initial Kr/Ar/F2 composition, the code calculates the densities of 24 species subject to over 100 reactions with 1-D spatial resolution (typically 16 zones) along the longitudinal lasing axis. Enthalpy accounting for each process is performed to partition the energy into internal, thermal, and radiative components. The electron as well as the heavy particle temperatures are followed for energy conservation and excitation rates. Transport of the lasing photons is performed along the axis on a dense subgrid using the method of characteristics. Amplified spontaneous emission is calculated using a discrete ordinates approach and includes contributions to the local intensity from the whole amplifier volume. Specular reflection off side walls and the rear mirror are included. Results of the model will be compared with data from the NRL NIKE laser and other published results.

A Photonic Crystal Laser from Solution Based Organo-Lead Iodide Perovskite Thin Films.

PubMed

Chen, Songtao; Roh, Kwangdong; Lee, Joonhee; Chong, Wee Kiang; Lu, Yao; Mathews, Nripan; Sum, Tze Chien; Nurmikko, Arto

2016-04-26

Perovskite semiconductors are actively investigated for high performance solar cells. Their large optical absorption coefficient and facile solution-based, low-temperature synthesis of thin films make perovskites also a candidate for light-emitting devices across the visible and near-infrared. Specific to their potential as optical gain medium for lasers, early work has demonstrated amplified spontaneous emission and lasing at attractively low thresholds of photoexcitation. Here, we take an important step toward practically usable perovskite lasers where a solution-processed thin film is embedded within a two-dimensional photonic crystal resonator. We demonstrate high degree of temporally and spatially coherent lasing whereby well-defined directional emission is achieved near 788 nm wavelength at optical pumping energy density threshold of 68.5 ± 3.0 μJ/cm(2). The measured power conversion efficiency and differential quantum efficiency of the perovskite photonic crystal laser are 13.8 ± 0.8% and 35.8 ± 5.4%, respectively. Importantly, our approach enables scalability of the thin film lasers to a two-dimensional multielement pixelated array of microlasers which we demonstrate as a proof-of-concept for possible projection display applications.

2-micron lasing in Tm:Lu2O3 ceramic: initial operation

NASA Astrophysics Data System (ADS)

Vetrovec, John; Filgas, David M.; Smith, Carey A.; Copeland, Drew A.; Litt, Amardeep S.; Briscoe, Eldridge; Schirmer, Ernestina

2018-03-01

We report on initial lasing of Tm:Lu2O3 ceramic laser with tunable output in the vicinity of 2 μm. Tm:Lu2O3 ceramic gain materials offer a much lower saturation fluence than the traditionally used Tm:YLF and Tm:YAG materials. The gain element is pumped by 796 nm diodes via a "2-for-1" crossrelaxation energy transfer mechanism, which enables high efficiency. The high thermal conductivity of the Lu2O3 host ( 18% higher than YAG) in combination with low quantum defect of 20% supports operation at high-average power. Konoshima's ceramic fabrication process overcomes the scalability limits of single crystal sesquioxides. Tm:Lu2O3 offers wide-bandwidth amplification of ultrashort pulses in a chirped-pulse amplification (CPA) system. A laser oscillator was continuously tuned over a 230 nm range from 1890 to 2120 nm while delivering up to 43W QCW output with up to 37% efficiency. This device is intended for initial testing and later seeding of a multi-pass edge-pumped disk amplifier now being developed by Aqwest which uses composite Tm:Lu2O3 disk gain elements.

Transverse-type laser assembly using induced electrical discharge excitation and method

DOEpatents

Ault, Earl R.

1994-01-01

A transverse-type laser assembly is disclosed herein. This assembly defines a laser cavity containing a vapor or gaseous substance which lases when subjected to specific electrical discharge excitation between a pair of spaced-apart electrodes located within the cavity in order to produce a source of light. An arrangement located entirely outside the laser cavity is provided for inducing a voltage across the electrodes within the cavity sufficient to provide the necessary electrical discharge excitation to cause a vapor substance between the electrodes to lase.

Transverse-type laser assembly using induced electrical discharge excitation and method

DOEpatents

Ault, E.R.

1994-04-19

A transverse-type laser assembly is disclosed herein. This assembly defines a laser cavity containing a vapor or gaseous substance which lases when subjected to specific electrical discharge excitation between a pair of spaced-apart electrodes located within the cavity in order to produce a source of light. An arrangement located entirely outside the laser cavity is provided for inducing a voltage across the electrodes within the cavity sufficient to provide the necessary electrical discharge excitation to cause a vapor substance between the electrodes to lase. 3 figures.

Three key regimes of single pulse generation per round trip of all-normal-dispersion fiber lasers mode-locked with nonlinear polarization rotation.

PubMed

Smirnov, Sergey; Kobtsev, Sergey; Kukarin, Sergey; Ivanenko, Aleksey

2012-11-19

We show experimentally and numerically new transient lasing regime between stable single-pulse generation and noise-like generation. We characterize qualitatively all three regimes of single pulse generation per round-trip of all-normal-dispersion fiber lasers mode-locked due to effect of nonlinear polarization evolution. We study spectral and temporal features of pulses produced in all three regimes as well as compressibility of such pulses. Simple criteria are proposed to identify lasing regime in experiment.

BRIEF COMMUNICATIONS: Dynamics of lasing of two TEA CO2 lasers coupled by a nonlinear SF6 cell

NASA Astrophysics Data System (ADS)

Baranov, V. Yu; Dyad'kin, A. P.; Shpilyun, O. V.

1991-10-01

A study was made of the kinetics of stimulated emission from two TEA CO2 lasers in a system with frequency locking by phase conjugation as a result of a four-wave interaction of light [V. Yu. Baranov, A. P. Dyad'kin, V. V. Likhanskiĭ et al., Sov. J. Quantum Electron. 18, 1462 (1988)]. A simple method for ensuring two-pulse lasing with a variable time delay between the pulses in one gas-discharge chamber was proposed.

Photodegradation of near-infrared-pumped Tm(3+)-doped ZBLAN fiber upconversion lasers.

PubMed

Booth, I J; Archambault, J L; Ventrudo, B F

1996-03-01

Photodegradation has been observed in Tm(3+)-doped ZBLAN fiber lasers pumped with laser diodes at 1135 nm. After upconversion lasing at 482 nm, the fiber develops color centers that absorb strongly at wavelengths below ~650 nm, affecting further upconversion lasing. The rate of damage formation is strongly dependent on the pump power level and on the thulium concentration. The color centers are bleached by intense blue light but recover with thermal excitation and can be removed by thermal annealing at temperature near 100 degrees C.

Tunable, continuous-wave Ti:sapphire channel waveguide lasers written by femtosecond and picosecond laser pulses.

PubMed

Grivas, Christos; Corbari, Costantino; Brambilla, Gilberto; Lagoudakis, Pavlos G

2012-11-15

Fabrication and cw lasing at 798.25 nm is reported for femtosecond (fs) and picosecond (ps) laser-inscribed channel waveguides in Ti:sapphire crystals. Lasing in channels written by fs (ps) pulses was obtained above a threshold of 84 mW (189 mW) with a maximum output power and a slope efficiency of 143 mW (45 mW) and 23.5% (7.1%), respectively. The emission wavelength was tuned over a 170 nm range by using a birefringent filter in an external cavity.

Self-assembled DNA tetrahedral optofluidic lasers with precise and tunable gain control.

PubMed

Chen, Qiushu; Liu, Huajie; Lee, Wonsuk; Sun, Yuze; Zhu, Dan; Pei, Hao; Fan, Chunhai; Fan, Xudong

2013-09-07

We have applied self-assembled DNA tetrahedral nanostructures for the precise and tunable control of the gain in an optofluidic fluorescence resonance energy transfer (FRET) laser. By adjusting the ratio of the donor and the acceptor attached to the tetrahedral vertices, 3.8 times reduction in the lasing threshold and 28-fold enhancement in the lasing efficiency were demonstrated. This work takes advantage of the self-recognition and self-assembly capabilities of biomolecules with well-defined structures and addressability, enabling nano-engineering of the laser down to the molecular level.

Cascaded Raman lasing in packaged high quality As₂S₃ microspheres.

PubMed

Vanier, Francis; Peter, Yves-Alain; Rochette, Martin

2014-11-17

We report the observation of cascaded Raman lasing in high-Q As₂S₃microspheres. Cascaded stimulated Raman scattering emission is obtained up to the 5th order for a pump wavelength of 1557 nm and up to the 3rd order for a pump wavelength of 1880 nm. High-Q As₂S₃microspheres are used in a self-frequency locking laser setup without an external laser source. Threshold curves measurements are presented and follow the expected coupled mode theory behavior with a sub-mW threshold pump power.

Cautionary note concerning the CuSO4 X-ray laser. [alternative to lasing action

NASA Technical Reports Server (NTRS)

Billman, K. W.; Mark, H.

1973-01-01

For the so far unconfirmed lasing action claimed by Kepros et al. (1972) to have been obtained by focusing a 1.06-micron radiation of a q-switched Nd(3+) glass laser to a small cylindrical volume inside a CuSO4-doped gelatin medium supported between two glass plates, an alternate explanation is proposed that does not depend on the assumption of laser action in copper. The proposed explanation shows how collimated X-ray beams might be created under the experimental conditions described by Kepros et al.

Apparatus for improving the working time of the XeBr laser

DOEpatents

Sander, R.K.; Balog, G.; Seegmiller, E.T.

1980-03-04

In XeBr lasers which make use of HBr as the source of bromine, it has been found that the working life of the laser is limited because of dissociation of the HBr in the lasing region to form H/sub 2/ and Br/sub 2/. Accordingly, apparatus is disclosed for substantially improving the working time of the XeBr laser wherein means are provided for recombining H/sub 2/ and Br/sub 2/ into HBr and for continuously circulating the gaseous working medium from the lasing region through the recombination region.

Apparatus for millimeter-wave signal generation

DOEpatents

Vawter, G. Allen; Hietala, Vincent M.; Zolper, John C.; Mar, Alan; Hohimer, John P.

1999-01-01

An opto-electronic integrated circuit (OEIC) apparatus is disclosed for generating an electrical signal at a frequency .gtoreq.10 GHz. The apparatus, formed on a single substrate, includes a semiconductor ring laser for generating a continuous train of mode-locked lasing pulses and a high-speed photodetector for detecting the train of lasing pulses and generating the electrical signal therefrom. Embodiments of the invention are disclosed with an active waveguide amplifier coupling the semiconductor ring laser and the high-speed photodetector. The invention has applications for use in OEICs and millimeter-wave monolithic integrated circuits (MMICs).

Explanation of the cw operation of the Er3+ 3-μm crystal laser

NASA Astrophysics Data System (ADS)

Pollnau, M.; Graf, Th.; Balmer, J. E.; Lüthy, W.; Weber, H. P.

1994-05-01

A computer simulation of the Er3+ 3-μm crystal laser considering the full rate-equation scheme up to the 4F7/2 level has been performed. The influence of the important system parameters on lasing and the interaction of these parameters has been clarified with multiple-parameter variations. Stimulated emission is fed mainly by up-conversion from the lower laser level and in many cases is reduced by the quenching of the lifetime of this level. However, also without up-conversion a set of parameters can be found that allows lasing. Up-conversion from the upper laser level is detrimental to stimulated emission but may be compensated by cross relaxation from the 4S3/2 level. For a typical experimental situation we started with the parameters of Er3+:LiYF4. In addition, the host materials Y3Al5O12 (YAG), YAlO3, Y3Sc2Al3O12 (YSGG), and BaY2F8, as well as the possibilities of codoping, are discussed. In view of the consideration of all excited levels up to 4F7/2, all lifetimes and branching ratios, ground-state depletion, excited-state absorption, three up-conversion processes as well as their inverse processes, stimulated emission, and a realistic resonator design, this is, to our knowledge, the most detailed investigation of the Er3+ 3-μm crystal laser performed so far.

Mode control in photonic crystal surface emitting lasers (PCSELs) through in-plane feedback (Conference Presentation)

NASA Astrophysics Data System (ADS)

Taylor, Richard J. E.; Li, Guangrui; Ivanov, Pavlo; Childs, David T. D.; Stevens, Ben J.; Babazadeh, Nasser; Ignatova, Olesya; Hogg, Richard A.

2017-02-01

All-semiconductor photonic crystal surface-emitting lasers (PCSELs) operating in CW mode at room temperature and coherently coupled arrays of these lasers are reviewed. These PCSELs are grown via MOVPE on GaAs substrates and include QW active elements and GaAs/InGaP photonic crystal (PC) layer situated above this active zone. Atoms of triangular shapes have been shown to increase optical power from the PCSEL but are also shown to result in a competition between lasing modes. Simulation shows that the energy splitting of lasing modes is smaller for triangular atoms, than for circles making high power single-mode devices difficult to achieve. In this work we experimentally investigate the effect of lateral optical feedback introduced by a facet cleave along one or two perpendicular PCSEL edges. This cleavage plane is misaligned to the PC resulting in a periodic variation of facet phase along the side of the device. Results confirm that a single cleave selects the lowest threshold 2D lasing mode, resulting in a 20% reduction in threshold current and favours single-mode emission. The addition of a second cleave at right-angles to the first has no significant effect upon threshold current. The virgin device is shown to have a symmetric far-field (1 degree) whilst a single cleave produces a 1 degree divergence perpendicular to cleave and 5 degree parallel to cleave. The second orthogonal cleave results in the far field becoming symmetric again but with a divergence angle of 1 degree indicating that single-mode lasing is supported over a wider area.

Theory and modelling of light-matter interactions in photonic crystal cavity systems coupled to quantum dot ensembles

NASA Astrophysics Data System (ADS)

Cartar, William K.

Photonic crystal microcavity quantum dot lasers show promise as high quality-factor, low threshold lasers, that can be integrated on-chip, with tunable room temperature opera- tions. However, such semiconductor microcavity lasers are notoriously difficult to model in a self-consistent way and are primarily modelled by simplified rate equation approxima- tions, typically fit to experimental data, which limits investigations of their optimization and fundamental light-matter interaction processes. Moreover, simple cavity mode optical theory and rate equations have recently been shown to fail in explaining lasing threshold trends in triangular lattice photonic crystal cavities as a function of cavity size, and the potential impact of fabrication disorder is not well understood. In this thesis, we develop a simple but powerful numerical scheme for modelling the quantum dot active layer used for lasing in these photonic crystal cavity structures, as an ensemble of randomly posi- tioned artificial two-level atoms. Each two-level atom is defined by optical Bloch equations solved by a quantum master equation that includes phenomenological pure dephasing and an incoherent pump rate that effectively models a multi-level gain system. Light-matter in- teractions of both passive and lasing structures are analyzed using simulation defined tools and post-simulation Green function techniques. We implement an active layer ensemble of up to 24,000 statistically unique quantum dots in photonic crystal cavity simulations, using a self-consistent finite-difference time-domain method. This method has the distinct advantage of capturing effects such as dipole-dipole coupling and radiative decay, without the need for any phenomenological terms, since the time-domain solution self-consistently captures these effects. Our analysis demonstrates a powerful ability to connect with recent experimental trends, while remaining completely general in its set-up; for example, we do not invoke common approximations such as the rotating-wave or slowly-varying envelope approximations, and solve dynamics with zero a priori knowledge.

Calculation of photonic bandgap for 2D hexagonal and square structure base on hybrid polymer material

NASA Astrophysics Data System (ADS)

Hidayat, S.; Riveli, N.

2018-05-01

We have calculated 2D photonic crystal band gap using plane-wave expansion method. The studied model of structures is hexagonal lattice and square lattice of rod cylinder in air. We have simulated the dispersion relation of it structure using hybrid polymer as rod material. The parameter structures are nrod = 1.5, nhole = 1, and rrod = 0.25a, where a is lattice constant. We found the distributed feedback occurs at the edge of upper band or frequency at 0.66 (a/λ). In our experimental work, we have successfully fabricated the 2D photonic crystal from hybrid polymer incorporated with organic dye laser. The lasing characteristics ware investigated using strip-line excitation light of SHG Nd-YAG laser (λ=532 nm). The lasing wavelengths for hexagonal structure are observed at 606 nm and 621 nm for photonic crystal period of 400 nm and 410 nm, respectively. λ=532 nm). Whereas the square structure, the lasing wavelengths are observed at (588 nm ± 2) and (606 nm ± 2 nm) for grating period of 391 nm and 405 nm.

Temporal complexity in emission from Anderson localized lasers

NASA Astrophysics Data System (ADS)

Kumar, Randhir; Balasubrahmaniyam, M.; Alee, K. Shadak; Mujumdar, Sushil

2017-12-01

Anderson localization lasers exploit resonant cavities formed due to structural disorder. The inherent randomness in the structure of these cavities realizes a probability distribution in all cavity parameters such as quality factors, mode volumes, mode structures, and so on, implying resultant statistical fluctuations in the temporal behavior. Here we provide direct experimental measurements of temporal width distributions of Anderson localization lasing pulses in intrinsically and extrinsically disordered coupled-microresonator arrays. We first illustrate signature exponential decays in the spatial intensity distributions of the lasing modes that quantify their localized character, and then measure the temporal width distributions of the pulsed emission over several configurations. We observe a dependence of temporal widths on the disorder strength, wherein the widths show a single-peaked, left-skewed distribution in extrinsic disorder and a dual-peaked distribution in intrinsic disorder. We propose a model based on coupled rate equations for an emitter and an Anderson cavity with a random mode structure, which gives excellent quantitative and qualitative agreement with the experimental observations. The experimental and theoretical analyses bring to the fore the temporal complexity in Anderson-localization-based lasing systems.

LASE Measurements of Water Vapor, Aerosol, and Cloud Distributions in Saharan Air Layers and Tropical Disturbances

NASA Technical Reports Server (NTRS)

Ismail, Syed; Ferrare, Richard; Browell, Edward; Kooi, Susan; Notari, Anthony; Butler, Carolyn; Burton, Sharon; Fenn, Marta; Krishnamurti, T. N.; Dunion, Jason;

A wavelength-tunable fiber laser using a novel filter based on a compound interference effect

NASA Astrophysics Data System (ADS)

Zou, Hui; Lou, Shuqin; Su, Wei; Han, Bolin; Shen, Xiao

2015-01-01

A wavelength-tunable erbium-doped fiber laser is proposed and experimentally demonstrated by using a novel filter which is formed from a 2  ×  2 3 dB multimode coupler incorporating a segment of polarization maintaining fiber (PMF). By using the filter with 2.1 m lengths of PMF in a ring fiber laser, a stable single wavelength lasing is obtained experimentally. Its 3 dB bandwidth is less than 0.0147 nm and the side mode suppression ratio (SMSR) is higher than 58.91 dB. Experimental results demonstrate that mode competition can be effectively suppressed and the SMSR can be improved due to the compound interference effect aroused by the novel filter. Meanwhile the stability of the output lasing can be enhanced. By appropriately adjusting the polarization controllers (PCs), the output lasing wavelength can be tuned from 1563.51 to 1568.21 nm. This fiber laser has the advantage of a simple structure and stable operation at room temperature.

Laser utilizing a gaseous lasing medium and method for operating the same

DOEpatents

Zerr, Bruce A.

1986-01-01

The invention relates to an improvement in gas lasers and a method of operating the same. In one aspect, the invention is an improved method for operating a high-power gas laser. The improvement comprises introducing the gas lasing medium tangentially to the laser tube at a pressure establishing a forced vortex in the tube. The vortex defines an axially extending core region characterized by a low pressure and temperature relative to the gas inlet and the exterior of the vortex. An electrical discharge is established in the core region to initiate lasing of the gas. The gas discharge from the tube is passed through a diffuser. As in conventional gas lasers, firing results in a very abrupt increase in gas temperature and in severe disruption of the gas. However, the gas vortex almost immediately restores the gas to its pre-firing condition. That is, almost all of the waste heat is transferred radially to the laser wall, and the original gas-flow pattern is restored. As a result, the power output of the laser is increased significantly, and the laser firing repetition rate is markedly increased.

Laser utilizing a gaseous lasing medium and method for operating the same

DOEpatents

Zerr, B.A.

1983-10-18

The invention relates to an improvement in gas lasers and a method of operating the same. In one aspect, the invention is an improved method for operating a high-power gas laser. The improvement comprises introducing the gas lasing medium tangentially to the laser tube at a pressure establishing a forced vortex in the tube. The vortex defines an axially extending core region characterized by a low pressure and temperature relative to the gas inlet and the exterior of the vortex. An electrical discharge is established in the core region to initiate lasing of the gas. The gas discharge from the tube is passed through a diffuser. As in conventional gas lasers, firing results in a very abrupt increase in gas temperature and in severe disruption of the gas. However, the gas vortex, almost immediately restores the gas to its prefiring condition. That is, almost all of the waste heat is transferred radially to the laser wall, and the original gas-flow pattern is restored. As a result, the power output of the laser is increased significantly, and the laser firing repetition rate is markedly increased.

Switchable multi-wavelength erbium-doped fiber ring laser based on a tapered in-line Mach–Zehnder interferometer

NASA Astrophysics Data System (ADS)

Zhou, Yuxin; Wang, Xin; Tang, Zijuan; Lou, Shuqin

2018-05-01

In this paper, a switchable multi-wavelength erbium-doped fiber ring laser based on a tapered in-line Mach–Zehnder interferometer is proposed. The in-line Mach–Zehnder interferometer is fabricated by splicing a large-core fiber between two segments of single mode fibers, in which the first splicing point is tapered and the second splicing point is connected directly. By carefully rotating the polarization controller, switchable single-, dual-, triple- and quad-wavelength lasing outputs can be obtained with a side mode suppression ratio higher than 50 dB. The maximal peak power difference of multi-wavelength lasing is 3.67 dB, demonstrating a good power equalization performance. Furthermore, the proposed laser is proven to be very stable at room temperature. The wavelength shifts and peak power fluctuations are less than 0.02 nm and 1.3 dB over half an hour. In addition, stable quintuple-wavelength lasing with a side mode suppression ratio higher than 50 dB can also be realized when the filter length is changed.

Laser interferometric studies of thermal effects of diode-pumped solid state lasing medium

NASA Astrophysics Data System (ADS)

Peng, Xiaoyuan; Asundi, Anand K.; Xu, Lei; Chen, Yihong; Xiong, Zhengjun; Lim, Gnian Cher

2000-04-01

Thermal effects dramatically influence the laser performance of diode-pumped solid state lasers (DPSSL). There are three factors accounting for thermal effects in diode-pumped laser medium: the change of the refractive index due to temperature gradient, the change of the refractive index due to thermal stress, and the change of the physical length due to thermal expansion (end effect), in which the first two effects can be called as thermal parts. A laser interferometer is proposed to measure both the bulk and physical messages of solid-state lasing medium. There are two advantages of the laser interferometry to determine the thermal lensing effect. One is that it allows separating the average thermal lens into thermal parts and end effect. Another is that the laser interferometry provides a non- invasive, full field, high-resolution means of diagnosing such effects by measuring the optical path difference induced by thermal loading in a lasing crystal reliable without disturbing the normal working conditions of the DPSS laser. Relevant measurement results are presented in this paper.

Unidirectional, dual-comb lasing under multiple pulse formation mechanisms in a passively mode-locked fiber ring laser

NASA Astrophysics Data System (ADS)

Liu, Ya; Zhao, Xin; Hu, Guoqing; Li, Cui; Zhao, Bofeng; Zheng, Zheng

2016-09-01

Dual-comb lasers from which asynchronous ultrashort pulses can be simultaneously generated have recently become an interesting research subject. They could be an intriguing alternative to the current dual-laser optical-frequency-comb source with highly sophisticated electronic control systems. If generated through a common light path traveled by all pulses, the common-mode noises between the spectral lines of different pulse trains could be significantly reduced. Therefore, coherent dual-comb generation from a completely common-path, unidirectional lasing cavity would be an interesting territory to explore. In this paper, we demonstrate such a dual-comb lasing scheme based on a nanomaterial saturable absorber with additional pulse narrowing and broadening mechanisms concurrently introduced into a mode-locked fiber laser. The interactions between multiple soliton formation mechanisms result in unusual bifurcation into two-pulse states with quite different characteristics. Simultaneous oscillation of pulses with four-fold difference in pulsewidths and tens of Hz repetition rate difference is observed. The coherence between these spectral-overlapped, picosecond and femtosecond pulses is further verified by the corresponding asynchronous cross-sampling and dual-comb spectroscopy measurements.

Coaxial GaAs-AlGaAs core-multishell nanowire lasers with epitaxial gain control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stettner, T., E-mail: Thomas.Stettner@wsi.tum.de, E-mail: Gregor.Koblmueller@wsi.tum.de, E-mail: Jonathan.Finley@wsi.tum.de; Zimmermann, P.; Loitsch, B.

2016-01-04

We demonstrate the growth and single-mode lasing operation of GaAs-AlGaAs core-multishell nanowires (NW) with radial single and multiple GaAs quantum wells (QWs) as active gain media. When subject to optical pumping lasing emission with distinct s-shaped input-output characteristics, linewidth narrowing and emission energies associated with the confined QWs are observed. Comparing the low temperature performance of QW NW laser structures having 7 coaxial QWs with a nominally identical structure having only a single QW shows that the threshold power density reduces several-fold, down to values as low as ∼2.4 kW/cm{sup 2} for the multiple QW NW laser. This confirms that themore » individual radial QWs are electronically weakly coupled and that epitaxial design can be used to optimize the gain characteristics of the devices. Temperature-dependent investigations show that lasing prevails up to 300 K, opening promising new avenues for efficient III–V semiconductor NW lasers with embedded low-dimensional gain media.« less

Effects of carbon dioxide, Nd:YAG and carbon dioxide-Nd:YAG combination lasers at high energy densities on synthetic hydroxyaptite.

PubMed

Meurman, J H; Voegel, J C; Rauhamaa-Mäkinen, R; Gasser, P; Thomann, J M; Hemmerle, J; Luomanen, M; Paunio, I; Frank, R M

1992-01-01

The aim of this study was to determine the crystalline structure and chemical alterations of synthetic hydroxyapatite after irradiation with either CO2, Nd:YAG or CO2-Nd:YAG combination lasers at high energy densities of 500-3,230 J.cm2. Further, dissolution kinetics of the lased material were analysed and compared with those of unlased apatite. Electron microscopy showed that the lased material consisted of two kinds of crystals. From the micrographs their diameters varied from 600 to 1,200 A and from 3,000 to 6,000 A, respectively. The larger crystals showed 6.9-Angström periodic lattice fringes in the transmission electron microscope. alpha-Tricalcium phosphate (TCP) was identified by X-ray diffraction. Selective-area electron diffraction identified the large crystals to consist of tricalcium phosphate while the smaller crystals were probably hydroxyapatite. Assays of dissolution kinetics showed that at these high energy densities lased material dissolved more rapidly than unlased synthetic hydroxyapatite due to the higher solubility of TCP.

Temperature dependence of material gain of InGaAsP/InP nano-heterostructure

NASA Astrophysics Data System (ADS)

Yadav, Rashmi; Alvi, P. A.

2014-04-01

This paper deals with temperature dependent study on material gain of InGaAsP/InP lasing nano-heterostructure with in TE mode. The model is based on simple separate confinement heterostructure (SCH). Material gain for the structure has been simulated for below and above the room temperatures. Different behaviors of the material gain for both ranges of the temperature have been reported in this paper. The results obtained in the simulation of the heterostructures suggest that only the shift in maximum gain takes place that appears at the lasing wavelength ˜ 1.40 μm.

Synthetic guide star generation

DOEpatents

Payne, Stephen A [Castro Valley, CA; Page, Ralph H [Castro Valley, CA; Ebbers, Christopher A [Livermore, CA; Beach, Raymond J [Livermore, CA

2008-06-10

A system for assisting in observing a celestial object and providing synthetic guide star generation. A lasing system provides radiation at a frequency at or near 938 nm and radiation at a frequency at or near 1583 nm. The lasing system includes a fiber laser operating between 880 nm and 960 nm and a fiber laser operating between 1524 nm and 1650 nm. A frequency-conversion system mixes the radiation and generates light at a frequency at or near 589 nm. A system directs the light at a frequency at or near 589 nm toward the celestial object and provides synthetic guide star generation.

Enhancement of collective atomic recoil lasing due to pump phase modulation

NASA Astrophysics Data System (ADS)

Robb, G. R. M.; Burgess, R. T. L.; Firth, W. J.

2008-10-01

We investigate the effect of a phase-modulated pump beam on collective backscattering [also termed collective atomic recoil lasing (CARL)] by a cold, collisionless atomic gas. We show using a numerical analysis that different regimes can be identified in which the atomic dynamics evolves in a qualitatively different manner during the light-atom interaction, depending on the magnitude of the pump modulation frequency. Our results also demonstrate that phase-modulating the pump field can substantially enhance the backscattered field intensity relative to the case of a monochromatic pump which has been used in CARL experiments to date.

Apparatus for improving the working time of the XeBr laser

DOEpatents

Sander, Robert K.; Balog, George; Seegmiller, Emma T.

1982-01-01

In XeBr lasers which make use of HBr as the source of bromine, it has been found that the working life of the laser is limited because of dissociation of the HBr in the lasing region to form H.sub.2 and Br.sub.2. Accordingly, apparatus is disclosed for substantially improving the working time of the XeBr laser wherein means are provided for recombining H.sub.2 and Br.sub.2 into HBr and for continuously circulating the gaseous working medium from the lasing region through the recombination region. BACKGROUND OF THE INVENTION

Fibre laser based on tellurium-doped active fibre

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alyshev, S V; Ryumkin, K E; Shubin, A V

2014-02-28

We have studied the lasing properties of tellurium-doped germanosilicate fibre, identified its gain and excited-state absorption bands, and assessed the effect of cooling to low temperature (77 K) on the bands. The excitation spectrum of the near-IR luminescence in the fibre has been measured. Lasing at 1.55 mm has been demonstrated for the first time in this gain medium at liquidnitrogen temperature and pump wavelengths of 1.064 and 1.085 mm. The measured Raman spectrum of the fibre provides some insight into the structure of the near-IR luminescence centre. (letters)

Bismuth-doped optical fibres: A new breakthrough in near-IR lasing media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dianov, Evgenii M

Recent results demonstrate that bismuth-doped optical fibres have considerable potential as near-IR active lasing media. This paper examines bismuth-doped fibres intended for the fabrication of fibre lasers and optical amplifiers and reviews recent results on the luminescence properties of various types of bismuth-doped fibres and the performance of bismuth-doped fibre lasers and optical amplifiers for the spectral range 1150 - 1550 nm. Problems are discussed that have yet to be solved in order to improve the efficiency of the bismuth lasers and optical amplifiers. (optical fibres, lasers and amplifiers. properties and applications)

Design of all-optical memory cell using EIT and lasing without inversion phenomena in optical micro ring resonators

NASA Astrophysics Data System (ADS)

Pasyar, N.; Yadipour, R.; Baghban, H.

2017-07-01

The proposed design of the optical memory unit cell contains dual micro ring resonators in which the effect of lasing without inversion (LWI) in three-level nano particles doped over the optical resonators or integrators as the gain segment is used for loss compensation. Also, an on/off phase shifter based on electromagnetically induced transparency (EIT) in three-level quantum dots (QDs) has been used for data reading at requested time. Device minimizing for integrated purposes and high speed data storage are the main advantages of the optical integrator based memory.

Circularly polarized lasing in chiral modulated semiconductor microcavity with GaAs quantum wells

NASA Astrophysics Data System (ADS)

Demenev, A. A.; Kulakovskii, V. D.; Schneider, C.; Brodbeck, S.; Kamp, M.; Höfling, S.; Lobanov, S. V.; Weiss, T.; Gippius, N. A.; Tikhodeev, S. G.

2016-10-01

We report close to circularly polarized lasing at ℏ ω = 1.473 and 1.522 eV from an AlAs/AlGaAs Bragg microcavity, with 12 GaAs quantum wells in the active region and chirally etched upper distributed Bragg refractor under optical pump at room temperature. The advantage of using the chiral photonic crystal with a large contrast of dielectric permittivities is its giant optical activity, allowing to fabricate a very thin half-wave plate, with a thickness of the order of the emitted light wavelength, and to realize the monolithic control of circular polarization.

History of chemical oxygen-iodine laser (COIL) development in the USA

NASA Astrophysics Data System (ADS)

Truesdell, Keith A.; Helms, Charles A.; Hager, Gordon D.

1994-09-01

This is an overview of the development of Chemical Oxygen-Iodine Laser (COIL) technology in the United States. Key technical developments will be reviewed, beginning in 1960 and culminating in 1977 with the first COIL lasing demonstration at the Air Force Weapons Laboratory (now the Phillips Laboratory). The discussion will then turn to subsonic laser development, supersonic lasing demonstration and efficiency improvements, and finishing with a brief discussion of some spin off COIL technologies. Particular emphasis will be placed on how the O2 (1(Delta) ) generator and O2-I2 mixing nozzle technologies evolved.

History of chemical oxygen-iodine laser (COIL) development in the USA

NASA Astrophysics Data System (ADS)

Truesdell, Keith A.; Helms, Charles A.; Hager, Gordon D.

1995-03-01

This is an overview of the development of Chemical Oxygen-Iodine Laser (COIL) technology in the United States. Key technical developments will be reviewed, beginning in 1960 and culminating in 1977 with the first COIL lasing demonstration at the Air Force Weapons Laboratory (now the Phillips Laboratory). The discussion will then turn to subsonic laser development, supersonic lasing demonstration and efficiency improvements, and finishing with a brief discussion of some spin off COIL technologies. Particular emphasis will be placed on how the O2 (1(Delta) ) generator and O2-I2 mixing nozzle technologies evolved.

Spectrally narrowed lasing of a self-injection KrF excimer laser

NASA Astrophysics Data System (ADS)

Shimada, Yasuhiro; Wani, Koichi; Miki, Tadaaki; Kawahara, Hidehito; Mimasu, Mutsumi; Ogata, Yoshiro

1990-08-01

Spectrally nantwed lasing of a KrF excimer laser has teen ahieved by a self-injection technique using abeam splitter for power extraction aixi intravity etalons for spectral-narrowing. The laser cavity is divithi into an amplifying branch aix! a spectralnarrowing branch. The spectral bandwidth was narrowed to <3pm FWHM with air-sed etalons placed in the spectral-narrowing branch. A laser propagation model was intrOdUced for describing the laser intensity traveling in the laser cavity. The calculated intensityincident onthe intracavityetalons wassmaller thanthat in theconventional Fabry-Perotcavity withplane-parallel mirrors.

Synthetic guide star generation

DOEpatents

Payne, Stephen A.; Page, Ralph H.; Ebbers, Christopher A.; Beach, Raymond J.

2004-03-09

A system for assisting in observing a celestial object and providing synthetic guide star generation. A lasing system provides radiation at a frequency at or near 938 nm and radiation at a frequency at or near 1583 nm. The lasing system includes a fiber laser operating between 880 nm and 960 nm and a fiber laser operating between 1524 nm and 1650 nm. A frequency-conversion system mixes the radiation and generates light at a frequency at or near 589 nm. A system directs the light at a frequency at or near 589 nm toward the celestial object and provides synthetic guide star generation.

GaSbBi/GaSb quantum well laser diodes

NASA Astrophysics Data System (ADS)

Delorme, O.; Cerutti, L.; Luna, E.; Narcy, G.; Trampert, A.; Tournié, E.; Rodriguez, J.-B.

2017-05-01

We report on the structural and optical properties of GaSbBi single layers and GaSbBi/GaSb quantum well heterostructures grown by molecular beam epitaxy on GaSb substrates. Excellent crystal quality and room-temperature photoluminescence are achieved in both cases. We demonstrate laser operation from laser diodes with an active zone composed of three GaSb0.885Bi0.115/GaSb quantum wells. These devices exhibit continuous-wave lasing at 2.5 μm at 80 K, and lasing under pulsed operation at room-temperature near 2.7 μm.

Phosphate-core silica-clad Er/Yb-doped optical fiber and cladding pumped laser.

PubMed

Egorova, O N; Semjonov, S L; Velmiskin, V V; Yatsenko, Yu P; Sverchkov, S E; Galagan, B I; Denker, B I; Dianov, E M

2014-04-07

We present a composite optical fiber with a Er/Yb co-doped phosphate-glass core in a silica glass cladding as well as cladding pumped laser. The fabrication process, optical properties, and lasing parameters are described. The slope efficiency under 980 nm cladding pumping reached 39% with respect to the absorbed pump power and 28% with respect to the coupled pump power. Due to high doping level of the phosphate core optimal length was several times shorter than that of silica core fibers.

On the mechanism of transverse-mode beatings in a Fabry - Perot laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, N; Ledenev, V I

2010-06-23

The mechanism of emergence of fundamental-mode and first-mode beatings in the case of a step-wise increase in the pump rate is studied under the stationary single-mode lasing conditions. Investigation is based on the numerical solution of nonstationary wave equations in a resonator in the quasi-optic approximation and on the equation for a relaxation-type medium as well as on the use of the first two Hermite - Gaussian polynomials {psi}{sub 0,1}(x) to obtain the distribution projections I{sub 0,1}(t), g{sub 0,1}(t) of the radiation intensity and gain, respectively. It is shown that the transverse-mode beatings emerge at early stages of two-mode lasing,more » the appearance of radiation intensity oscillations in the active medium preceding the development of the gain oscillations. The time of the passage of two-mode lasing to the stationary regime is determined. The phase shift {pi}/2 between the oscillations I{sub 1}(t) and g{sub 1}(t) is found for the established beating regime and the modulation depth {Delta}I averaged over the output aperture of the radiation intensity in the established two-mode regime is shown to be proportional to the pump rate excess k over the single-mode lasing threshold. A scheme for controlling the mode composition of laser radiation is proposed, which is based on the rules for determining I{sub 0,1}(t) by the sensor signals. The efficiency of the scheme is studied. The scheme employs two field intensity sensors mounted inside the resonator behind the output aperture. (resonators. modes)« less

Lasing action from photonic bound states in continuum

NASA Astrophysics Data System (ADS)

Kodigala, Ashok; Lepetit, Thomas; Gu, Qing; Bahari, Babak; Fainman, Yeshaiahu; Kanté, Boubacar

2017-01-01

In 1929, only three years after the advent of quantum mechanics, von Neumann and Wigner showed that Schrödinger’s equation can have bound states above the continuum threshold. These peculiar states, called bound states in the continuum (BICs), manifest themselves as resonances that do not decay. For several decades afterwards the idea lay dormant, regarded primarily as a mathematical curiosity. In 1977, Herrick and Stillinger revived interest in BICs when they suggested that BICs could be observed in semiconductor superlattices. BICs arise naturally from Feshbach’s quantum mechanical theory of resonances, as explained by Friedrich and Wintgen, and are thus more physical than initially realized. Recently, it was realized that BICs are intrinsically a wave phenomenon and are thus not restricted to the realm of quantum mechanics. They have since been shown to occur in many different fields of wave physics including acoustics, microwaves and nanophotonics. However, experimental observations of BICs have been limited to passive systems and the realization of BIC lasers has remained elusive. Here we report, at room temperature, lasing action from an optically pumped BIC cavity. Our results show that the lasing wavelength of the fabricated BIC cavities, each made of an array of cylindrical nanoresonators suspended in air, scales with the radii of the nanoresonators according to the theoretical prediction for the BIC mode. Moreover, lasing action from the designed BIC cavity persists even after scaling down the array to as few as 8-by-8 nanoresonators. BIC lasers open up new avenues in the study of light-matter interaction because they are intrinsically connected to topological charges and represent natural vector beam sources (that is, there are several possible beam shapes), which are highly sought after in the fields of optical trapping, biological sensing and quantum information.

Lithographically Defined, Room Temperature Low Threshold Subwavelength Red-Emitting Hybrid Plasmonic Lasers.

PubMed

Liu, Ning; Gocalinska, Agnieszka; Justice, John; Gity, Farzan; Povey, Ian; McCarthy, Brendan; Pemble, Martyn; Pelucchi, Emanuele; Wei, Hong; Silien, Christophe; Xu, Hongxing; Corbett, Brian

2016-12-14

Hybrid plasmonic lasers provide deep subwavelength optical confinement, strongly enhanced light-matter interaction and together with nanoscale footprint promise new applications in optical communication, biosensing, and photolithography. The subwavelength hybrid plasmonic lasers reported so far often use bottom-up grown nanowires, nanorods, and nanosquares, making it difficult to integrate these devices into industry-relevant high density plasmonic circuits. Here, we report the first experimental demonstration of AlGaInP based, red-emitting hybrid plasmonic lasers at room temperature using lithography based fabrication processes. Resonant cavities with deep subwavelength 2D and 3D mode confinement of λ 2 /56 and λ 3 /199, respectively, are demonstrated. A range of cavity geometries (waveguides, rings, squares, and disks) show very low lasing thresholds of 0.6-1.8 mJ/cm 2 with wide gain bandwidth (610 nm-685 nm), which are attributed to the heterogeneous geometry of the gain material, the optimized etching technique, and the strong overlap of the gain material with the plasmonic modes. Most importantly, we establish the connection between mode confinements and enhanced absorption and stimulated emission, which plays critical roles in maintaining low lasing thresholds at extremely small hybrid plasmonic cavities. Our results pave the way for the further integration of dense arrays of hybrid plasmonic lasers with optical and electronic technology platforms.

Graphene based widely-tunable and singly-polarized pulse generation with random fiber lasers

PubMed Central

Yao, B. C.; Rao, Y. J.; Wang, Z. N.; Wu, Y.; Zhou, J. H.; Wu, H.; Fan, M. Q.; Cao, X. L.; Zhang, W. L.; Chen, Y. F.; Li, Y. R.; Churkin, D.; Turitsyn, S.; Wong, C. W.

2015-01-01

Pulse generation often requires a stabilized cavity and its corresponding mode structure for initial phase-locking. Contrastingly, modeless cavity-free random lasers provide new possibilities for high quantum efficiency lasing that could potentially be widely tunable spectrally and temporally. Pulse generation in random lasers, however, has remained elusive since the discovery of modeless gain lasing. Here we report coherent pulse generation with modeless random lasers based on the unique polarization selectivity and broadband saturable absorption of monolayer graphene. Simultaneous temporal compression of cavity-free pulses are observed with such a polarization modulation, along with a broadly-tunable pulsewidth across two orders of magnitude down to 900 ps, a broadly-tunable repetition rate across three orders of magnitude up to 3 MHz, and a singly-polarized pulse train at 41 dB extinction ratio, about an order of magnitude larger than conventional pulsed fiber lasers. Moreover, our graphene-based pulse formation also demonstrates robust pulse-to-pulse stability and wide-wavelength operation due to the cavity-less feature. Such a graphene-based architecture not only provides a tunable pulsed random laser for fiber-optic sensing, speckle-free imaging, and laser-material processing, but also a new way for the non-random CW fiber lasers to generate widely tunable and singly-polarized pulses. PMID:26687730

Graphene based widely-tunable and singly-polarized pulse generation with random fiber lasers.

PubMed

Yao, B C; Rao, Y J; Wang, Z N; Wu, Y; Zhou, J H; Wu, H; Fan, M Q; Cao, X L; Zhang, W L; Chen, Y F; Li, Y R; Churkin, D; Turitsyn, S; Wong, C W

2015-12-21

Pulse generation often requires a stabilized cavity and its corresponding mode structure for initial phase-locking. Contrastingly, modeless cavity-free random lasers provide new possibilities for high quantum efficiency lasing that could potentially be widely tunable spectrally and temporally. Pulse generation in random lasers, however, has remained elusive since the discovery of modeless gain lasing. Here we report coherent pulse generation with modeless random lasers based on the unique polarization selectivity and broadband saturable absorption of monolayer graphene. Simultaneous temporal compression of cavity-free pulses are observed with such a polarization modulation, along with a broadly-tunable pulsewidth across two orders of magnitude down to 900 ps, a broadly-tunable repetition rate across three orders of magnitude up to 3 MHz, and a singly-polarized pulse train at 41 dB extinction ratio, about an order of magnitude larger than conventional pulsed fiber lasers. Moreover, our graphene-based pulse formation also demonstrates robust pulse-to-pulse stability and wide-wavelength operation due to the cavity-less feature. Such a graphene-based architecture not only provides a tunable pulsed random laser for fiber-optic sensing, speckle-free imaging, and laser-material processing, but also a new way for the non-random CW fiber lasers to generate widely tunable and singly-polarized pulses.

2D Ruddlesden-Popper Perovskites Microring Laser Array.

PubMed

Zhang, Haihua; Liao, Qing; Wu, Yishi; Zhang, Zhaoyi; Gao, Qinggang; Liu, Peng; Li, Meili; Yao, Jiannian; Fu, Hongbing

2018-04-01

3D organic-inorganic hybrid perovskites have featured high gain coefficients through the electron-hole plasma stimulated emission mechanism, while their 2D counterparts of Ruddlesden-Popper perovskites (RPPs) exhibit strongly bound electron-hole pairs (excitons) at room temperature. High-performance solar cells and light-emitting diodes (LEDs) are reported based on 2D RPPs, whereas light-amplification devices remain largely unexplored. Here, it is demonstrated that ultrafast energy transfer along cascade quantum well (QW) structures in 2D RPPs concentrates photogenerated carriers on the lowest-bandgap QW state, at which population inversion can be readily established enabling room-temperature amplified spontaneous emission and lasing. Gain coefficients measured for 2D RPP thin-films (≈100 nm in thickness) are found about at least four times larger than those for their 3D counterparts. High-density large-area microring arrays of 2D RPPs are fabricated as whispering-gallery-mode lasers, which exhibit high quality factor (Q ≈ 2600), identical optical modes, and similarly low lasing thresholds, allowing them to be ignited simultaneously as a laser array. The findings reveal that 2D RPPs are excellent solution-processed gain materials potentially for achieving electrically driven lasers and ideally for on-chip integration of nanophotonics. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fluorene- and benzofluorene-cored oligomers as low threshold and high gain amplifying media

NASA Astrophysics Data System (ADS)

Kazlauskas, Karolis; Kreiza, Gediminas; Bobrovas, Olegas; AdomÄ--nienÄ--, Ona; AdomÄ--nas, Povilas; Jankauskas, Vygintas; JuršÄ--nas, Saulius

2015-07-01

Deliberate control of intermolecular interactions in fluorene- and benzofluorene-cored oligomers was attempted via introduction of different-length alkyl moieties to attain high emission amplification and low amplified spontaneous emission (ASE) threshold at high oligomer concentrations. Containing fluorenyl peripheral groups decorated with different-length alkyl moieties, the oligomers were found to express weak concentration quenching of emission, yet excellent carrier drift mobilities (close to 10-2 cm2/V/s) in the amorphous films. Owing to the larger radiative decay rates (>1.0 × 109 s-1) and smaller concentration quenching, fluorene-cored oligomers exhibited down to one order of magnitude lower ASE thresholds at higher concentrations as compared to those of benzofluorene counterparts. The lowest threshold (300 W/cm2) obtained for the fluorene-cored oligomers at the concentration of 50 wt % in polymer matrix is among the lowest reported for solution-processed amorphous films in ambient conditions, what makes the oligomers promising for lasing application. Great potential in emission amplification was confirmed by high maximum net gain (77 cm-1) revealed for these compounds. Although the photostability of the oligomers was affected by photo-oxidation, it was found to be comparable to that of various organic lasing materials including some commercial laser dyes evaluated under similar excitation conditions.

Photonics and application of dipyrrinates in the optical devices

NASA Astrophysics Data System (ADS)

Aksenova, Iu; Bashkirtsev, D.; Prokopenko, A.; Kuznetsova, R.; Dudina, N.; Berezin, M.

2016-08-01

In this paper spectral-luminescent, lasing, photochemical, and sensory characteristics of a number of Zn(II) and B(III) coordination complexes with dipyrrinates with different structures are presented. We have discussed relations of the structure of investigated compounds and formed solvates with their optical characteristics. The results showed that alkyl substituted dipyrrinates derivatives have excellent luminescent characteristics and demonstrated effective lasing upon excitation of Nd:YAG-laser. They can be used as active media for liquid tunable lasers. Zinc and boron fluoride complexes of dipyrrinates with heavy atoms in structure don't have fluorescence but have long-lived emission due to increased nonradiative intersystem processes in the excited state by the mechanism of a heavy atom. For solid samples based on halogenated complexes was found dependency of the long-lived emission intensity of the oxygen concentration in gas flow. The presence of line segment indicates the possibility of the use of these complexes as a basis for creation of optical sensors for oxygen. Moreover, results of a study of halogen-substituted aza-complexes under irradiation are presented. Such complexes are promising for the creating media for generation of singlet oxygen (1O2), which is important for photodynamic therapy in medicine and photocatalytic reactions in the industry.

Fusion reactor pumped laser

DOEpatents

Jassby, D.L.

1987-09-04

A nuclear pumped laser capable of producing long pulses of very high power laser radiation is provided. A toroidal fusion reactor provides energetic neutrons which are slowed down by a moderator. The moderated neutrons are converted to energetic particles capable of pumping a lasing medium. The lasing medium is housed in an annular cell surrounding the reactor. The cell includes an annular reflecting mirror at the bottom and an annular output window at the top. A neutron reflector is disposed around the cell to reflect escaping neutrons back into the cell. The laser radiation from the annular window is focused onto a beam compactor which generates a single coherent output laser beam. 10 figs.

Fusion reactor pumped laser

DOEpatents

Jassby, Daniel L.

1988-01-01

A nuclear pumped laser capable of producing long pulses of very high power laser radiation is provided. A toroidal fusion reactor provides energetic neutrons which are slowed down by a moderator. The moderated neutrons are converted to energetic particles capable of pumping a lasing medium. The lasing medium is housed in an annular cell surrounding the reactor. The cell includes an annular reflecting mirror at the bottom and an annular output window at the top. A neutron reflector is disposed around the cell to reflect escaping neutrons back into the cell. The laser radiation from the annular window is focused onto a beam compactor which generates a single coherent output laser beam.

Proton-transfer lasers based on solid copolymers of modified 2-(2'-hydroxyphenyl)benzimidazoles with methacrylate monomers

NASA Astrophysics Data System (ADS)

Costela, A.; García-Moreno, I.; Mallavia, Ricardo; Amat-Guerri, F.; Barroso, J.; Sastre, R.

1998-06-01

We report on the lasing action of two newly synthesized 2-(2'-hydroxyphenyl) benzimidazole derivatives copolymerized with methyl methacrylate. The laser samples were transversely pumped with a N 2 laser at 337 nm. The influence on the proton-transfer laser performance of the distance between the chromophore group and the polymeric main chain and of the rigidity of the polymeric host matrix, were studied. Significant increases in lasing efficiency and photostability are demonstrated for some of the new materials, as compared to those previously obtained with related proton-transfer dyes also covalently bound to methacrylic monomers.

Nonreciprocal lasing in topological cavities of arbitrary geometries

NASA Astrophysics Data System (ADS)

Bahari, Babak; Ndao, Abdoulaye; Vallini, Felipe; El Amili, Abdelkrim; Fainman, Yeshaiahu; Kanté, Boubacar

2017-11-01

Resonant cavities are essential building blocks governing many wave-based phenomena, but their geometry and reciprocity fundamentally limit the integration of optical devices. We report, at telecommunication wavelengths, geometry-independent and integrated nonreciprocal topological cavities that couple stimulated emission from one-way photonic edge states to a selected waveguide output with an isolation ratio in excess of 10 decibels. Nonreciprocity originates from unidirectional edge states at the boundary between photonic structures with distinct topological invariants. Our experimental demonstration of lasing from topological cavities provides the opportunity to develop complex topological circuitry of arbitrary geometries for the integrated and robust generation and transport of photons in classical and quantum regimes.

The effect of p-doping on multi-state lasing in InAs/InGaAs quantum dot lasers for different cavity lengths

NASA Astrophysics Data System (ADS)

Korenev, V. V.; Savelyev, A. V.; Maximov, M. V.; Zubov, F. I.; Shernyakov, Yu M.; Zhukov, A. E.

2017-11-01

The effect of modulation p-doping on multi-state lasing in InAs/InGaAs quantum dot (QD) lasers is studied for different levels of acceptor concentration. It is shown that in case of the short laser cavities, p-doping results in higher output power of the ground-state optical transitions of InAs/InGaAs QDs whereas in longer samples p-doping may result in the decrease of this power component. On the basis of this observation, the optimal design of laser active region and optimal doping level are discussed in details.

Tunable multiwavelength fiber laser based on a θ-shaped microfiber filter

NASA Astrophysics Data System (ADS)

Li, Yue; Xu, Zhilin; Luo, Yiyang; Xiang, Yang; Yan, Zhijun; Liu, Deming; Sun, Qizhen

2018-06-01

We propose and experimentally demonstrate a flexibly tunable multiwavelength fiber ring laser based on a θ-shaped microfiber filter in conjunction with an erbium-doped fiber amplifier. The stable operation of the multiwavelength lasing is successfully achieved at room temperature, with the peak power fluctuation less than 0.519 dB. By micro-adjusting the cavity length of the filter, the channel spacing can be independently tuned within the gain range of the optical amplifier. We have achieved 0.084 nm-spacing 48 channel, 0.147 nm-spacing 25 channel, 0.190 nm-spacing 20 channel and 0.302 nm-spacing 15 channel lasing wavelengths at room temperature.

Cascaded Raman lasing in a PM phosphosilicate fiber with random distributed feedback

NASA Astrophysics Data System (ADS)

Lobach, Ivan A.; Kablukov, Sergey I.; Babin, Sergey A.

2018-02-01

We report on the first demonstration of a linearly polarized cascaded Raman fiber laser based on a simple half-open cavity with a broadband composite reflector and random distributed feedback in a polarization maintaining phosphosilicate fiber operating beyond zero dispersion wavelength ( 1400 nm). With increasing pump power from a Yb-doped fiber laser at 1080 nm, the random laser generates subsequently 8 W at 1262 nm and 9 W at 1515 nm with polarization extinction ratio of 27 dB. The generation linewidths amount to about 1 nm and 3 nm, respectively, being almost independent of power, in correspondence with the theory of a cascaded random lasing.

Efficient, diode-pumped Tm3+:BaY2F8 vibronic laser

NASA Astrophysics Data System (ADS)

Cornacchia, F.; Parisi, D.; Bernardini, C.; Toncelli, A.; Tonelli, M.

2004-05-01

In this work we report the spectroscopy and laser results of several Thulium doped BaY2F8 single crystals grown using the Czochralski technique. The doping concentration is between 2at.% and 18at.%. We performed room temperature laser experiments pumping the samples with a laser diode at 789 nm obtaining 61% as maximum optical-to-optical efficiency with a maximum output power of 290 mW and a minimum lasing threshold of 26 mW. The lasing wavelength changed with the dopant concentration from 1927 nm up to 2030 nm and the nature of the transition changed from purely electronic to vibronic, accordingly.

Tunable optofluidic microring laser based on a tapered hollow core microstructured optical fiber.

PubMed

Li, Zhi-Li; Zhou, Wen-Yuan; Luo, Ming-Ming; Liu, Yan-Ge; Tian, Jian-Guo

2015-04-20

A tunable optofluidic microring dye laser within a tapered hollow core microstructured optical fiber was demonstrated. The fiber core was filled with a microfluidic gain medium plug and axially pumped by a nanosecond pulse laser at 532 nm. Strong radial emission and low-threshold lasing (16 nJ/pulse) were achieved. Lasing was achieved around the surface of the microfluidic plug. Laser emission was tuned by changing the liquid surface location along the tapered fiber. The possibility of developing a tunable laser within the tapered simplified hollow core microstructured optical fiber presents opportunities for developing liquid surface position sensors and biomedical analysis.

Coherent random lasing controlled by Brownian motion of the active scatterer

NASA Astrophysics Data System (ADS)

Liang, Shuofeng; Yin, Leicheng; Zhang, ZhenZhen; Xia, Jiangying; Xie, Kang; Zou, Gang; Hu, Zhijia; Zhang, Qijin

2018-05-01

The stability of the scattering loop is fundamental for coherent random lasing in a dynamic scattering system. In this work, fluorescence of DPP (N, N-di [3-(isobutyl polyhedral oligomeric silsesquioxanes) propyl] perylene diimide) is scattered to produce RL and we realize the transition from incoherent RL to coherent RL by controlling the Brownian motion of the scatterers (dimer aggregates of DPP) and the stability of scattering loop. To produce coherent random lasers, the loop needs to maintain a stable state within the loop-stable time, which can be determined through controlled Brownian motion of scatterers in the scattering system. The result shows that the loop-stable time is within 5.83 × 10‑5 s to 1.61 × 10‑4 s based on the transition from coherent to incoherent random lasing. The time range could be tuned by finely controlling the viscosity of the solution. This work not only develops a method to predict the loop-stable time, but also develops the study between Brownian motion and random lasers, which opens the road to a variety of novel interdisciplinary investigations involving modern statistical mechanics and disordered photonics.

High power tube solid-state laser with zigzag propagation of pump and laser beam

NASA Astrophysics Data System (ADS)

Savich, Michael

2015-02-01

A novel resonator and pumping design with zigzag propagation of pumping and laser beams permits to design an improved tube Solid State Laser (SSL), solving the problem of short absorption path to produce a high power laser beam (100 - 1000kW). The novel design provides an amplifier module and laser oscillator. The tube-shaped SSL includes a gain element fiber-optically coupled to a pumping source. The fiber optic coupling facilitates light entry at compound Brewster's angle of incidence into the laser gain element and uses internal reflection to follow a "zigzag" path in a generally spiral direction along the length of the tube. Optics are arranged for zigzag propagation of the laser beam, while the cryogenic cooling system is traditional. The novel method of lasing uses advantages of cylindrical geometry to reach the high volume of gain medium with compactness and structural rigidity, attain high pump density and uniformity, and reach a low threshold without excessive increase of the temperature of the crystal. The design minimizes thermal lensing and stress effects, and provides high gain amplification, high power extraction from lasing medium, high pumping and lasing efficiency and a high beam quality.

Reduced dimer production in solar-simulator-pumped continuous wave iodine lasers based on model simulations and scaling and pumping studies

NASA Technical Reports Server (NTRS)

Costen, Robert C.; Heinbockel, John H.; Miner, Gilda A.; Meador, Willard E., Jr.; Tabibi, Bagher M.; Lee, Ja H.; Williams, Michael D.

1995-01-01

A numerical rate equation model for a continuous wave iodine laser with longitudinally flowing gaseous lasant is validated by approximating two experiments that compare the perfluoroalkyl iodine lasants n-C3F7I and t-C4F9I. The salient feature of the simulations is that the production rate of the dimer (C4F9)2 is reduced by one order of magnitude relative to the dimer (C3F7)2. The model is then used to investigate the kinetic effects of this reduced dimer production, especially how it improves output power. Related parametric and scaling studies are also presented. When dimer production is reduced, more monomer radicals (t-C4F9) are available to combine with iodine ions, thus enhancing depletion of the laser lower level and reducing buildup of the principal quencher, molecular iodine. Fewer iodine molecules result in fewer downward transitions from quenching and more transitions from stimulated emission of lasing photons. Enhanced depletion of the lower level reduces the absorption of lasing photons. The combined result is more lasing photons and proportionally increased output power.

Wavelength tunable single nanowire lasers based on surface plasmon polariton enhanced Burstein-Moss effect.

PubMed

Liu, Xinfeng; Zhang, Qing; Yip, Jing Ngei; Xiong, Qihua; Sum, Tze Chien

2013-01-01

Wavelength tunable semiconductor nanowire (NW) lasers are promising for multifunctional applications ranging from optical communication to spectroscopy analysis. Here, we present a demonstration of utilizing the surface plasmon polariton (SPP) enhanced Burstein-Moss (BM) effect to tune the lasing wavelength of a single semiconductor NW. The photonic lasing mode of the CdS NW (with length ~10 μm and diameter ~220 nm) significantly blue shifts from 504 to 483 nm at room temperature when the NW is in close proximity to the Au film. Systematic steady state power dependent photoluminescence (PL) and time-resolved PL studies validate that the BM effect in the hybrid CdS NW devices is greatly enhanced as a consequence of the strong coupling between the SPP and CdS excitons. With decreasing dielectric layer thickness h from 100 to 5 nm, the enhancement of the BM effect becomes stronger, leading to a larger blue shift of the lasing wavelength. Measurements of enhanced exciton emission intensities and recombination rates in the presence of Au film further support the strong interaction between SPP and excitons, which is consistent with the simulation results.

All-Optical Switching and Two-States Light-Controlled Coherent-Incoherent Random Lasing in a Thiophene-Based Donor-Acceptor System.

PubMed

Szukalski, Adam; Ayadi, Awatef; Haupa, Karolina; El-Ghayoury, Abdelkrim; Sahraoui, Bouchta; Mysliwiec, Jaroslaw

2018-03-30

We describe herein the synthesis and characterization of a thiophene-based donor-acceptor system, namely (E)-2-(4-nitrostyryl)-5-phenylthiophene (Th-pNO 2 ), which was prepared under Horner-Wadsworth-Emmons conditions. The UV/Vis absorption bands, including the intramolecular charge transfer (ICT) band, were fully assigned using DFT and TD-DFT computations. The results of both efficient third-order nonlinear optical properties and light-amplification phenomena are presented. Investigations of photoinduced birefringence (PIB) in optical Kerr effect (OKE) experiments showed a great potential for this particular compound as an efficient, fully reversible, and fast optical switch. Time constants for the observed trans-cis-trans molecular transitions are in the range of microseconds and give a competitive experimental result for the well-known and exploited azobenzene derivatives. Random lasing (RL) investigations confirmed that this organic system is potentially useful to achieve strong light enhancement, observed as a multimode lasing action. Both RL and OKE measurements indicate that this material is a representative of thiophene derivatives, which can be utilized to fabricate fast all-optical switches or random lasers (light amplifiers). © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Two kinds of novel tunable Thulium-doped fiber laser

NASA Astrophysics Data System (ADS)

Ma, Xiaowei; Chen, Daru; Feng, Gaofeng; Yang, Junyong

2014-11-01

Two kinds of tunable Thulium-doped fiber laser (TDFL) respectively using a Sagnac loop mirror and a novel tunable multimode interference (MMI) fiber filter are experimentally demonstrated. The TDFL with the Sagnac loop mirror made by a 145.5-cm polarization-maintaining fiber (PMF) can operate with stable dual-wavelength lasing or tunable single-wavelength lasing around 1860nm. Both stable dual-wavelength and tunable single-wavelength lasing are achieved by adjusting a polarization controller in the Sagnac loop mirror. The TDFL with a novel tunable MMI fiber filter formed by splicing a segment of a special no-core fiber that is an all silica fiber without fiber core to single mode fibers can achieve tuning range from 1813.52 nm to 1858.70 nm. The no-core fiber with a large diameter of 200 μm is gradually vertically covered by refractive index matching liquid, which leads to a wavelength tuning of the transmission peak of the MMI fiber filter. The relationship between the refractive index of the refractive index matching liquid and the peak wavelength shift of the MMI fiber filter is also discussed. Using the MMI fiber filter, a Thulium-doped fiber laser with a tuning range of 45.18 nm is demonstrated.

Conjugated polymer-titania nanoparticle hybrid films: random lasing action and ultrasensitive detection of explosive vapors.

PubMed

Deng, Changmin; He, Qingguo; He, Chao; Shi, Liqi; Cheng, Jiangong; Lin, Tong

2010-04-08

We have first demonstrated that a random laser action generated by a hybrid film composed of a semiconducting organic polymer (SOP) and TiO(2) nanoparticles can be used to detect 2,4,6-trinitrotoluene (TNT) vapors. The hybrid film was fabricated by spin-casting SOP solution dispersed with nanosized TiO(2) particles on quartz glass. The SOP in the hybrid film functioned as both the gain medium and the sensory transducer. A random lasing action was observed with a certain pump power when the size (diameter of 50 nm) and concentration (8.9 x 10(12)/cm(3)) of TiO(2) nanoparticles were optimized. Measurements of fluorescence quenching behavior of the hybrid film in TNT vapor atmosphere (10 ppb) showed that attenuated lasing in optically pumped hybrid film displayed a sensitivity to vapors of explosives more than 20 times higher than was observed from spontaneous emission. This phenomenon has been explained with the four-level laser model. Since the sensory transducer used in the hybrid polymer/nanoparticles system could be replaced by other functional materials, the concept developed could be extended to more general domains of chemical or environment detection.

Commissioning of a kW-class nanosecond pulsed DPSSL operating at 105 J, 10 Hz

NASA Astrophysics Data System (ADS)

Mason, Paul; Divoký, Martin; Butcher, Thomas; Pilař, Jan; Ertel, Klaus; Hanuš, Martin; De Vido, Mariastefania; Banerjee, Saumyabrata; Phillips, Jonathan; Smith, Jodie; Hollingham, Ian; Muresan, Mihai-George; Landowski, Brian; Suarez-Merchan, Jorge; Thomas, Adrian; Dominey, Mark; Benson, Luke; Lintern, Andrew; Costello, Billy; Tomlinson, Stephanie; Blake, Steve; Tyldesley, Mike; Lucianetti, Antonio; Hernandez-Gomez, Cristina; Edwards, Chris; Mocek, Tomas; Collier, John

2017-05-01

In this paper we present details of the commissioning of DiPOLE100, a kW-class nanosecond pulsed diode pumped solid state laser (DPSSL), at the HiLASE Centre at Dolní Břežany in the Czech Republic. The laser system, built at the Central Laser Facility (CLF), was dismantled, packaged, shipped and reassembled at HiLASE over a 12 month period by a collaborative team from the CLF and HiLASE. First operation of the laser at the end of 2016 demonstrated amplification of 10 ns pulses at 10 Hz pulse repetition rate to an energy of 105 J at 1029.5 nm, representing the world's first kW average power, high-energy, nanosecond pulsed DPSSL. To date DiPOLE100 has been operated for over 2.5 hours at energies in excess of 100 J at 10 Hz, corresponding to nearly 105 shots, and has demonstrated long term energy stability of less than 1% RMS for continuous operation over 1 hour. This confirms the power scalability of multislab cryogenic gas-cooled amplifier technology and demonstrates its potential as a laser driver for next generation scientific, industrial, and medical applications.

Super low threshold plasmonic WGM lasing from an individual ZnO hexagonal microrod on an Au substrate for plasmon lasers.

PubMed

Dong, H M; Yang, Y H; Yang, G W

2015-03-05

We demonstrate an individual ZnO hexagonal microrod on the surface of an Au substrate which can become new sources for manufacturing miniature ZnO plasmon lasers by surface plasmon polariton coupling to whispering-gallery modes (WGMs). We also demonstrate that the rough surface of Au substrates can acquire a more satisfied enhancement of ZnO emission if the surface geometry of Au substrates is appropriate. Furthermore, we achieve high Q factor and super low threshold plasmonic WGM lasing from an individual ZnO hexagonal microrod on the surface of the Au substrate, in which Q factor can reach 5790 and threshold is 0.45 KW/cm(2) which is the lowest value reported to date for ZnO nanostructures lasing, at least 10 times smaller than that of ZnO at the nanometer. Electron transfer mechanisms are proposed to understand the physical origin of quenching and enhancement of ZnO emission on the surface of Au substrates. These investigations show that this novel coupling mode holds a great potential of ZnO hexagonal micro- and nanorods for data storage, bio-sensing, optical communications as well as all-optic integrated circuits.

Continuous-wave operation of m-plane GaN-based vertical-cavity surface-emitting lasers with a tunnel junction intracavity contact

NASA Astrophysics Data System (ADS)

Forman, Charles A.; Lee, SeungGeun; Young, Erin C.; Kearns, Jared A.; Cohen, Daniel A.; Leonard, John T.; Margalith, Tal; DenBaars, Steven P.; Nakamura, Shuji

2018-03-01

We have achieved continuous-wave (CW) operation of an optically polarized m-plane GaN-based vertical-cavity surface-emitting laser (VCSEL) with an ion implanted current aperture, a tunnel junction intracavity contact, and a dual dielectric distributed Bragg reflector design. The reported VCSEL has 2 quantum wells, with a 14 nm quantum well width, 1 nm barriers, a 5 nm electron-blocking layer, and a 23 λ total cavity thickness. The thermal performance was improved by increasing the cavity length and using Au-In solid-liquid interdiffusion bonding, which led to lasing under CW operation for over 20 min. Lasing wavelengths under pulsed operation were observed at 406 nm, 412 nm, and 419 nm. Only the latter two modes appeared under CW operation due to the redshifted gain at higher temperatures. The peak output powers for a 6 μm aperture VCSEL under CW and pulsed operation were 140 μW and 700 μW, respectively. The fundamental transverse mode was observed without the presence of filamentary lasing. The thermal impedance was estimated to be ˜1400 °C/W for a 6 μm aperture 23 λ VCSEL.

Optical phase conjugation: principles, techniques, and applications

NASA Astrophysics Data System (ADS)

He, Guang S.

2002-05-01

Over the last three decades, optical phase conjugation (OPC) has been one of the major research subjects in the field of nonlinear optics and quantum electronics. OPC defines usually a special relationship between two coherent optical beams propagating in opposite directions with reversed wave front and identical transverse amplitude distributions. The unique feature of a pair of phase-conjugate beams is that the aberration influence imposed on the forward beam passed through an inhomogeneous or disturbing medium can be automatically removed for the backward beam passed through the same disturbing medium. To date there have been three major technical approaches that can efficiently produce the backward phase-conjugate beam. The first approach is based on the degenerate (or partially degenerate) four-wave mixing processes, the second is based on various backward simulated (Brillouin, Raman, Rayleigh-wing or Kerr) scattering processes, and the third is based on one-photon or multi-photon pumped backward stimulated emission (lasing) processes. Among these three different approaches, there is a common physical mechanism that plays the same essential role in generating a backward phase-conjugate beam, which is the formation of the induced holographic grating and the subsequent wave-front restoration via a backward reading beam. In most experimental studies, certain types of resonance enhancements of induced refractive-index changes are desirable for obtaining higher grating-refraction efficiency. The momentum of OPC studies has recently become even stronger because there are more prospective potentials and achievements for applications. OPC-associated techniques can be successfully utilized in many different application areas: such as high-brightness laser oscillator/amplifier systems, cavity-less lasing devices, laser target-aiming systems, aberration correction for coherent-light transmission and reflection through disturbing media, long distance optical fiber communications with ultra-high bit-rate, optical phase locking and coupling systems, and novel optical data storage and processing systems.

Optically-free-standing InGaN microdisks with metallic reflectors

NASA Astrophysics Data System (ADS)

Zhang, Xuhui; To, Chap Hang; Choi, Hoi Wai

2017-01-01

The optical properties of free-standing thin-film microdisks with NiAg metallic reflectors are compared with those with an indium tin oxide (ITO) interfacial layer. The microdisks have been fabricated by a combination of microsphere lithography and laser lift-off processes. Optical-pumped lasing from the microdisk with NiAg reflector has been observed, with reduced threshold and higher quality factor compared those with ITO layers, attributed to improved optical confinement due to the reflectivity of the Ag coating. The results are supported by three-dimensional (3D) finite-difference-time-domain (FDTD) simulations.

Solvent-free fluidic organic dye lasers.

PubMed

Choi, Eun Young; Mager, Loic; Cham, Tran Thi; Dorkenoo, Kokou D; Fort, Alain; Wu, Jeong Weon; Barsella, Alberto; Ribierre, Jean-Charles

2013-05-06

We report on the demonstration of liquid organic dye lasers based on 9-(2-ethylhexyl)carbazole (EHCz), so-called liquid carbazole, doped with green- and red-emitting laser dyes. Both waveguide and Fabry-Perot type microcavity fluidic organic dye lasers were prepared by capillary action under solvent-free conditions. Cascade Förster-type energy transfer processes from liquid carbazole to laser dyes were employed to achieve color-variable amplified spontaneous emission and lasing. Overall, this study provides the first step towards the development of solvent-free fluidic organic semiconducting lasers and demonstrates a new kind of optoelectronic applications for liquid organic semiconductors.

INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Two-stage liquid phase epitaxy for fabrication of buried InGaAsP/InP heterostructures

NASA Astrophysics Data System (ADS)

Procházková, O.; Novotný, J.; Šrobár, F.

1988-11-01

The technology of growth of buried heterojunction lasers emitting at 1.3 μm and some of their physical properties are described. Mesa stripes 8-μm wide were formed on heteroepitaxial wafers grown by liquid phase epitaxy at 630°C. They were buried by a second process at a lower temperature (590°C). The threshold current was about 100 mA and the temperature sensitivity was characterized by a parameter amounting to about 60 K. Single-mode lasing was observed occasionally.

Yb3+ sensitized Tm3+ upconversion in tellurite lead oxide glass.

PubMed

Mohanty, Deepak Kumar; Rai, Vineet Kumar; Dwivedi, Y

2012-04-01

Triply ionized thulium/thulium--ytterbium doped/codoped TeO2-Pb3O4 (TPO) glasses have been fabricated by classical quenching method. The upconversion emission spectra in the Tm3+/Tm3+-Yb3+ doped/codoped glasses upon excitation with a diode laser lasing at ∼980 nm has been studied. Effect of the addition of the Yb3+ on the upconversion emission intensity in the visible and near infrared regions of the Tm3+ doped in TPO glass has been studied and the processes involved explored. Copyright © 2011 Elsevier B.V. All rights reserved.

[INVITED] Coherent perfect absorption of electromagnetic wave in subwavelength structures

NASA Astrophysics Data System (ADS)

Yan, Chao; Pu, Mingbo; Luo, Jun; Huang, Yijia; Li, Xiong; Ma, Xiaoliang; Luo, Xiangang

2018-05-01

Electromagnetic (EM) absorption is a common process by which the EM energy is transformed into other kinds of energy in the absorber, for example heat. Perfect absorption of EM with structures at subwavelength scale is important for many practical applications, such as stealth technology, thermal control and sensing. Coherent perfect absorption arises from the interplay of interference and absorption, which can be interpreted as a time-reversed process of lasing or EM emitting. It provides a promising way for complete absorption in both nanophotonics and electromagnetics. In this review, we discuss basic principles and properties of a coherent perfect absorber (CPA). Various subwavelength structures including thin films, metamaterials and waveguide-based structures to realize CPAs are compared. We also discuss the potential applications of CPAs.

Laser ablation of single-crystalline silicon by radiation of pulsed frequency-selective fiber laser

NASA Astrophysics Data System (ADS)

Veiko, V. P.; Skvortsov, A. M.; Huynh, C. T.; Petrov, A. A.

2015-07-01

We have studied the process of destruction of the surface of a single-crystalline silicon wafer scanned by the beam of a pulsed ytterbium-doped fiber laser radiation with a wavelength of λ = 1062 nm. It is established that the laser ablation can proceed without melting of silicon and the formation of a plasma plume. Under certain parameters of the process (radiation power, beam scan velocity, and beam overlap density), pronounced oxidation of silicon microparticles with the formation of a characteristic loose layer of fine powdered silicon dioxide has been observed for the first time. The range of lasing and beam scanning regimes in which the growth of SiO2 layer takes place is determined.

Single mode terahertz quantum cascade amplifier

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, Y., E-mail: yr235@cam.ac.uk; Wallis, R.; Shah, Y. D.

2014-10-06

A terahertz (THz) optical amplifier based on a 2.9 THz quantum cascade laser (QCL) structure has been demonstrated. By depositing an antireflective coating on the QCL facet, the laser mirror losses are enhanced to fully suppress the lasing action, creating a THz quantum cascade (QC) amplifier. Terahertz radiation amplification has been obtained, by coupling a separate multi-mode THz QCL of the same active region design to the QC amplifier. A bare cavity gain is achieved and shows excellent agreement with the lasing spectrum from the original QCL without the antireflective coating. Furthermore, a maximum optical gain of ∼30 dB with single-modemore » radiation output is demonstrated.« less

Quantitative verification of ab initio self-consistent laser theory.

PubMed

Ge, Li; Tandy, Robert J; Stone, A D; Türeci, Hakan E

2008-10-13

We generalize and test the recent "ab initio" self-consistent (AISC) time-independent semiclassical laser theory. This self-consistent formalism generates all the stationary lasing properties in the multimode regime (frequencies, thresholds, internal and external fields, output power and emission pattern) from simple inputs: the dielectric function of the passive cavity, the atomic transition frequency, and the transverse relaxation time of the lasing transition.We find that the theory gives excellent quantitative agreement with full time-dependent simulations of the Maxwell-Bloch equations after it has been generalized to drop the slowly-varying envelope approximation. The theory is infinite order in the non-linear hole-burning interaction; the widely used third order approximation is shown to fail badly.

Instability of the Superfluid Flow as Black-Hole Lasing Effect.

PubMed

Finazzi, S; Piazza, F; Abad, M; Smerzi, A; Recati, A

2015-06-19

We show that the critical velocity of a superfluid flow through a penetrable barrier coincides with the onset of the analog black-hole lasing effect. This dynamical instability is triggered by modes resonating in an effective cavity formed by two horizons enclosing the barrier. The location of the horizons is set by v(x)=c(x), with v(x),c(x) being the local fluid velocity and sound speed, respectively. We compute the critical velocity analytically and show that it is univocally determined by the configuration of the horizons. In the limit of broad barriers, the continuous spectrum at the origin of the Hawking-like radiation and of the Landau energetic instability is recovered.

Solar-pumped electronic-to-vibrational energy transfer lasers

NASA Technical Reports Server (NTRS)

Harries, W. L.; Wilson, J. W.

1981-01-01

The possibility of using solar-pumped lasers as solar energy converters is examined. The absorbing media considered are halogens or halogen compounds, which are dissociated to yield excited atoms, which then hand over energy to a molecular lasing medium. Estimates of the temperature effects for a Br2-CO2-He system with He as the cooling gas are given. High temperatures can cause the lower energy levels of the CO2 laser transition to be filled. The inverted populations are calculated and lasing should be possible. However, the efficiency is less than 0.001. Examination of other halogen-molecular lasant combinations (where the rate coefficients are known) indicate efficiencies in all cases of less than 0.005.

Parasitic lasing suppression in large-aperture Ti:sapphire amplifiers by optimizing the seed-pump time delay

NASA Astrophysics Data System (ADS)

Chu, Y. X.; Liang, X. Y.; Yu, L. H.; Xu, L.; Lu, X. M.; Liu, Y. Q.; Leng, Y. X.; Li, R. X.; Xu, Z. Z.

2013-05-01

Theoretical and experimental investigations are carried out to determine the influence of the time delay between the input seed pulse and pump pulses on transverse parasitic lasing in a Ti:sapphire amplifier with a diameter of 80 mm, which is clad by a refractive index-matched liquid doped with an absorber. When the time delay is optimized, a maximum output energy of 50.8 J is achieved at a pump energy of 105 J, which corresponds to a conversion efficiency of 47.5%. Based on the existing compressor, the laser system achieves a peak power of 1.26 PW with a 29.0 fs pulse duration.

Self-cavity lasing in optically pumped single crystals of p-sexiphenyl

NASA Astrophysics Data System (ADS)

Yanagi, Hisao; Tamura, Kenji; Sasaki, Fumio

2016-08-01

Organic single-crystal self-cavities are prepared by solution growth of p-sexiphenyl (p-6P). Based on Fabry-Pérot feedback inside a quasi-lozenge-shaped platelet crystal, edge-emitting laser is obtained under optical pumping. The multimode lasing band appears at the 0-1 or 0-2 vibronic progressions depending on the excitation conditions which affect the self-absorption effect. Cavity-size dependence of amplified spontaneous emission (ASE) is investigated with laser-etched single crystals of p-6P. As the cavity length of square-shaped crystal is reduced from 100 to 10 μm, ASE threshold fluence is decreased probably due to size-dependent light confinement in the crystal cavity.

Optical spectroscopy of cobalt-doped cadmium telluride

NASA Astrophysics Data System (ADS)

Turner, Eric J.; Evans, Jonathan; Harris, Thomas

2018-02-01

Spectroscopic investigation of Co2+:CdTe was performed to evaluate it's potential as a lasing medium. The sample had a targeted doping concentration of 2% and measurements were performed from 10 - 120K. Cross-sections for Co:CdTe were calculated using Füchtbauer-Ladenburg and reciprocity methods. Calculations suggest the potential for efficient lasing at 3.7μm when pumped by a 3μm laser source on the 4A2 <-> 4T2 transition. The fluorescence lifetime was measured to quantify the temperature dependence of the non-radiative relaxation rate. This work aims to characterize Co:CdTe as a novel gain medium for compact, tunable mid-infrared lasers operating within the atmospheric transmission window.

Whispering gallery mode laser based on cholesteric liquid crystal microdroplets as temperature sensor

NASA Astrophysics Data System (ADS)

Zhao, Liyuan; Wang, Yan; Yuan, Yonggui; Liu, Yongjun; Liu, Shuangqiang; Sun, Weimin; Yang, Jun; Li, Hanyang

2017-11-01

We developed a tunable whispering gallery mode (WGM) microlaser based on dye-doped cholesteric liquid crystal (CLC) microdroplets with controllable size in an aqueous environment. An individual dye-doped CLC microdroplet confined at the tip of a microcapillary was optically pumped via a tapered optical fiber tip positioned within its vicinity. Numerical simulations and various spectral characteristics verify the WGM resonance of the lasing in microdroplets. Thermal tuning of the lasing modes is realized due to the thermo-optic effect of CLC. The proposed CLC microdroplet-based WGM resonator was applied as a temperature sensor and exhibited maximum temperature sensitivity up to 0.96 nm/°C.

Watt-level ~2 μm laser output in Tm3+-doped tungsten tellurite glass double-cladding fiber.

PubMed

Li, Kefeng; Zhang, Guang; Hu, Lili

2010-12-15

We report, for the first time to the best of our knowledge, a watt level cw fiber laser at ~2 μm from a piece of 40-cm-long newly developed highly thulium-doped (3.76 × 10(20) ions/cm(3)) tungsten tellurite glass double cladding fiber pumped by a commercial 800 nm laser diode. The maximum output power of the fiber laser reaches 1.12 W. The slope efficiency and the optical-optical efficiency with respect to the absorbed pump are 20% and 16%, respectively. The lasing threshold is 1.46 W, and the lasing wavelength is centered at 1937 nm.

Volume Bragg grating narrowed high-power and highly efficient cladding-pumped Raman fiber laser.

PubMed

Liu, Jun; Yao, Weichao; Zhao, Chujun; Shen, Deyuan; Fan, Dianyuan

2014-12-10

High-power and highly efficient operation of a single-mode cladding-pumped Raman fiber laser with narrow lasing bandwidth is demonstrated. The spectral narrowing was realized by an external cavity containing a volume Bragg grating with a center wavelength of 1658 nm. A maximum output power of 10.4 W at 1658.3 nm with a spectral linewidth (FWHM) of ∼0.1  nm was obtained for the launched pump power of 18.4 W, corresponding to a slope efficiency of 109% with respect to the launched pump power. Lasing characteristics of free-running operation are also evaluated and discussed.

Silicon/III-V laser with super-compact diffraction grating for WDM applications in electronic-photonic integrated circuits.

PubMed

Wang, Yadong; Wei, Yongqiang; Huang, Yingyan; Tu, Yongming; Ng, Doris; Lee, Cheewei; Zheng, Yunan; Liu, Boyang; Ho, Seng-Tiong

2011-01-31

We have demonstrated a heterogeneously integrated III-V-on-Silicon laser based on an ultra-large-angle super-compact grating (SCG). The SCG enables single-wavelength operation due to its high-spectral-resolution aberration-free design, enabling wavelength division multiplexing (WDM) applications in Electronic-Photonic Integrated Circuits (EPICs). The SCG based Si/III-V laser is realized by fabricating the SCG on silicon-on-insulator (SOI) substrate. Optical gain is provided by electrically pumped heterogeneous integrated III-V material on silicon. Single-wavelength lasing at 1550 nm with an output power of over 2 mW and a lasing threshold of around 150 mA were achieved.

Direct solar-pumped iodine laser amplifier

NASA Technical Reports Server (NTRS)

Han, K. S.

1986-01-01

During this period the parametric studies of the iodine laser oscillator pumped by a Vortek simulator were carried out before amplifier studies. The amplifier studies are postponed to the extended period after completing the parametric studies. In addition, the kinetic modeling of a solar-pumped iodine laser amplifier, and the experimental work for a solar pumped dye laser amplifier are in progress. This report contains three parts: (1) a 10 W CW iodine laser pumped by a Vortek solar simulator; (2) kinetic modeling to predict the time to lasing threshold, lasing time, and energy output of solar-pumped iodine laser; and (3) the study of the dye laser amplifier pumped by a Tamarack solar simulator.

Part Marking and Identification Materials' for MISSE

NASA Technical Reports Server (NTRS)

Roxby, Donald; Finckenor, Miria M.

2008-01-01

The Materials on International Space Station Experiment (MISSE) is being conducted with funding from NASA and the U.S. Department of Defense, in order to evaluate candidate materials and processes for flight hardware. MISSE modules include test specimens used to validate NASA technical standards for part markings exposed to harsh environments in low-Earth orbit and space, including: atomic oxygen, ultraviolet radiation, thermal vacuum cycling, and meteoroid and orbital debris impact. Marked test specimens are evaluated and then mounted in a passive experiment container (PEC) that is affixed to an exterior surface on the International Space Station (ISS). They are exposed to atomic oxygen and/or ultraviolet radiation for a year or more before being retrieved and reevaluated. Criteria include percent contrast, axial uniformity, print growth, error correction, and overall grade. MISSE 1 and 2 (2001-2005), MISSE 3 and 4 (2006-2007), and MISSE 5 (2005-2006) have been completed to date. Acceptable results were found for test specimens marked with Data Matrix(TradeMark) symbols by Intermec Inc. and Robotic Vision Systems Inc using: laser bonding, vacuum arc vapor deposition, gas assisted laser etch, chemical etch, mechanical dot peening, laser shot peening, laser etching, and laser induced surface improvement. MISSE 6 (2008-2009) is exposing specimens marked by DataLase(Registed TradeMark), Chemico technologies Inc., Intermec Inc., and tesa with laser-markable paint, nanocode tags, DataLase and tesa laser markings, and anodized metal labels.

High-pulse-energy 3.9-μm lasers in Ho:BYF

NASA Astrophysics Data System (ADS)

Stutz, Russell; Miller, Harold C.; Dinndorf, Kenneth M.; Cassanho, Arlete; Jenssen, Hans P.

2004-07-01

Experimental results describing pulsed lasers operating near 3.9 μm on the Ho3+ (5I5-5I6) transition in highly-doped (> 10 at. %) barium yttrium fluoride (BaY2F8 or BYF) will be presented. The 5I5 manifolds in Ho:BYF were pumped using a flashlamp excited, free-running Cr:LiSAF laser tuned to the Ho3+ absorption peak near 889nm. Ho3+ concentrations of 10%, 20%, 30% and 40% in BYF were lased in a simple end-pumped resonator. Some similar data was also obtained in 10% and 20% Ho:YLF. The highest 3.9 μm pulse energy obtained in the comparative study was 55 mJ (at ~10% optical-to-optical efficiency) using the 30% Ho:BYF crystal. A dual end-pumped laser in 30% Ho:BYF was also demonstrated, providing a pulse energy of 90 mJ in a near diffraction limited beam (M2 ~ 1.2). Emission decay data was taken to shed light on the observed dependence of laser efficiency on holmium concentration and excitation density. The lifetimes of both lasing levels (5I5 and 5I6) deviate rather significantly from their low-concentration values. Plausible energy transfer processes that may be responsible for the observed trends in the laser and emission data will also be discussed.

Compact compressive arc and beam switchyard for energy recovery linac-driven ultraviolet free electron lasers

NASA Astrophysics Data System (ADS)

Akkermans, J. A. G.; Di Mitri, S.; Douglas, D.; Setija, I. D.

2017-08-01

High gain free electron lasers (FELs) driven by high repetition rate recirculating accelerators have received considerable attention in the scientific and industrial communities in recent years. Cost-performance optimization of such facilities encourages limiting machine size and complexity, and a compact machine can be realized by combining bending and bunch length compression during the last stage of recirculation, just before lasing. The impact of coherent synchrotron radiation (CSR) on electron beam quality during compression can, however, limit FEL output power. When methods to counteract CSR are implemented, appropriate beam diagnostics become critical to ensure that the target beam parameters are met before lasing, as well as to guarantee reliable, predictable performance and rapid machine setup and recovery. This article describes a beam line for bunch compression and recirculation, and beam switchyard accessing a diagnostic line for EUV lasing at 1 GeV beam energy. The footprint is modest, with 12 m compressive arc diameter and ˜20 m diagnostic line length. The design limits beam quality degradation due to CSR both in the compressor and in the switchyard. Advantages and drawbacks of two switchyard lines providing, respectively, off-line and on-line measurements are discussed. The entire design is scalable to different beam energies and charges.

Monolithically Integrated High-β Nanowire Lasers on Silicon.

PubMed

Mayer, B; Janker, L; Loitsch, B; Treu, J; Kostenbader, T; Lichtmannecker, S; Reichert, T; Morkötter, S; Kaniber, M; Abstreiter, G; Gies, C; Koblmüller, G; Finley, J J

2016-01-13

Reliable technologies for the monolithic integration of lasers onto silicon represent the holy grail for chip-level optical interconnects. In this context, nanowires (NWs) fabricated using III-V semiconductors are of strong interest since they can be grown site-selectively on silicon using conventional epitaxial approaches. Their unique one-dimensional structure and high refractive index naturally facilitate low loss optical waveguiding and optical recirculation in the active NW-core region. However, lasing from NWs on silicon has not been achieved to date, due to the poor modal reflectivity at the NW-silicon interface. We demonstrate how, by inserting a tailored dielectric interlayer at the NW-Si interface, low-threshold single mode lasing can be achieved in vertical-cavity GaAs-AlGaAs core-shell NW lasers on silicon as measured at low temperature. By exploring the output characteristics along a detection direction parallel to the NW-axis, we measure very high spontaneous emission factors comparable to nanocavity lasers (β = 0.2) and achieve ultralow threshold pump energies ≤11 pJ/pulse. Analysis of the input-output characteristics of the NW lasers and the power dependence of the lasing emission line width demonstrate the potential for high pulsation rates ≥250 GHz. Such highly efficient nanolasers grown monolithically on silicon are highly promising for the realization of chip-level optical interconnects.

Design study of high gradient, low impedance accelerating structures for the FERMI free electron laser linac upgrade

NASA Astrophysics Data System (ADS)

Shafqat, N.; Di Mitri, S.; Serpico, C.; Nicastro, S.

2017-09-01

The FERMI free-electron laser (FEL) of Elettra Sincrotrone Trieste, Italy, is a user facility driven by a 1.5 GeV 10-50 Hz S-band radiofrequency linear accelerator (linac), and it is based on an external laser seeding scheme that allows lasing at the shortest fundamental wavelength of 4 nm. An increase of the beam energy to 1.8 GeV at a tolerable breakdown rate, and an improvement of the final beam quality is desired in order to allow either lasing at 4 nm with a higher flux, or lasing at shorter wavelengths. This article presents the impedance analysis of newly designed S-band accelerating structures, for replacement of the existing backward travelling wave structures (BTWS) in the last portion of the FERMI linac. The new structure design promises higher accelerating gradient and lower impedance than those of the existing BTWS. Particle tracking simulations show that, with the linac upgrade, the beam relative energy spread, its linear and nonlinear z-correlation internal to the bunch, and the beam transverse emittances can be made smaller than the ones in the present configuration, with expected advantage to the FEL performance. The repercussion of the upgrade on the linac quadrupole magnets setting, for a pre-determined electron beam optics, is also considered.

Semiconductor diode laser material and devices with emission in visible region of the spectrum

NASA Technical Reports Server (NTRS)

Ladany, I.; Kressel, H.

1975-01-01

Two alloy systems, (AlGa)As and (InGa)P, were studied for their properties relevant to obtaining laser diode operation in the visible region of the spectrum. (AlGa)As was prepared by liquid-phase epitaxy (LPE) and (InGa)P was prepared both by vapor-phase epitaxy and by liquid-phase epitaxy. Various schemes for LPE growth were applied to (InGa)P, one of which was found to be capable of producing device material. All the InGaP device work was done using vapor-phase epitaxy. The most successful devices were fabricated in (AlGa)As using heterojunction structures. At room temperature, the large optical cavity design yielded devices lasing in the red (7000 A). Because of the relatively high threshold due to the basic band structure limitation in this alloy, practical laser diode operation is presently limited to about 7300 A. At liquid-nitrogen temperature, practical continuous-wave operation was obtained at a wavelength of 6500 to 6600 A, with power emission in excess of 50 mW. The lowest pulsed lasing wavelength is 6280 A. At 223 K, lasing was obtained at 6770 A, but with high threshold currents. The work dealing with CW operation at room temperature was successful with practical operation having been achieved to about 7800 A.

Wrinkled 2D Materials: A Versatile Platform for Low-Threshold Stretchable Random Lasers.

PubMed

Hu, Han-Wen; Haider, Golam; Liao, Yu-Ming; Roy, Pradip Kumar; Ravindranath, Rini; Chang, Huan-Tsung; Lu, Cheng-Hsin; Tseng, Chang-Yang; Lin, Tai-Yung; Shih, Wei-Heng; Chen, Yang-Fang

2017-11-01

A stretchable, flexible, and bendable random laser system capable of lasing in a wide range of spectrum will have many potential applications in next- generation technologies, such as visible-spectrum communication, superbright solid-state lighting, biomedical studies, fluorescence, etc. However, producing an appropriate cavity for such a wide spectral range remains a challenge owing to the rigidity of the resonator for the generation of coherent loops. 2D materials with wrinkled structures exhibit superior advantages of high stretchability and a suitable matrix for photon trapping in between the hill and valley geometries compared to their flat counterparts. Here, the intriguing functionalities of wrinkled reduced graphene oxide, single-layer graphene, and few-layer hexagonal boron nitride, respectively, are utilized to design highly stretchable and wearable random laser devices with ultralow threshold. Using methyl-ammonium lead bromide perovskite nanocrystals (PNC) to illustrate the working principle, the lasing threshold is found to be ≈10 µJ cm -2 , about two times less than the lowest value ever reported. In addition to PNC, it is demonstrated that the output lasing wavelength can be tuned using different active materials such as semiconductor quantum dots. Thus, this study is very useful for the future development of high-performance wearable optoelectronic devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Temporal, thermal, and light stability of continuously tunable cholesteric liquid crystal laser array.

PubMed

Jeong, Mi-Yun; Chung, Ki Soo; Wu, Jeong Weon

2014-11-01

Fine-structured polymerized cholesteric liquid crystal (PCLC) wedge laser devices have been realized, with high fine spatial tunability of the lasing wavelength. With resolution less than 0.3 nm in a broad spectral range, more than one hundred laser lines could be obtained in a PCLC cell without extra devices. For practical device application, we studied the stability of the device in detail over time, and in response to strong external light sources, and thermal perturbation. The PCLC wedge cells had good temporal stability for 1 year and showed good stability for strong perturbations, with the lasing wavelength shifting less than 1 nm, while the laser peak intensities decreased by up to 34%, and the high energy band edge of the photonic band gap (PBG) was red shifted 3 nm by temperature perturbation. However, when we consider the entire lasing spectrum for the PCLC cell, the 1-nm wavelength shift may not matter. Although the laser peak intensities were decreased by up to 34% in total for all of the perturbation cases, the remaining 34% laser peak intensity is considerable extent to make use. This good stability of the PCLC laser device is due to the polymerization of the CLC by UV curing. This study will be helpful for practical CLC laser device development.

Dye lasing arrangement including an optical assembly for altering the cross-section of its pumping beam and method

DOEpatents

O'Neil, Richard W.; Sweatt, William C.

1992-01-01

An optical assembly is disclosed herein along with a method of operation for use in a dye lasing arrangement, for example a dye laser oscillator or a dye amplifier, in which a continuous stream of dye is caused to flow through a given zone in a cooperating dye chamber while the zone is being illuminated by light from a pumping beam which is directed into the given zone. This in turn causes the dye therein to lase and thereby produce a new dye beam in the case of a dye laser oscillator or amplify a dye beam in the case of a dye amplifier. The optical assembly so disclosed is designed to alter the pump beam such that the beam enters the dye chamber with a different cross-sectional configuration, preferably one having a more uniform intensity profile, than its initially produced cross-sectional configuration. To this end, the assembly includes a network of optical components which first act on the beam while the latter retains its initially produced cross-sectional configuration for separating it into a plurality of predetermined segments and then recombines the separated components in a predetermined way which causes the recombined beam to have the different cross-sectional configuration.

Laser supported reduction of specific microorganisms in the periodontal pocket with the aid of an Er,Cr:YSGG laser: a pilot study.

PubMed

Gutknecht, N; Van Betteray, C; Ozturan, S; Vanweersch, L; Franzen, R

2015-01-01

The aim of this study was to evaluate the effectiveness of a radial firing tip of an Er,Cr:YSGG laser as an adjunct to a nonsurgical periodontal treatment. Twelve patients with chronic or aggressive periodontitis were treated by conventional periodontal treatment using ultrasonic devices and hand instruments and, additionally, in two quadrants with an Er,Cr:YSGG laser. A new radial firing tip (RFPT 14-5, Biolase) was used with 1.5 W, 30 Hz, 11% air, 20% water, and pulse duration 140 μs. Microbiological smears were taken before treatment, one day after lasing, and three and six months after lasing. Pocket depths of all periodontal sites were measured before and six months after treatment. The total bacterial load of Prevotella intermedia, Tannerella forsythia, Treponema denticola, Fusobacterium nucleatum, Porphyromonas gingivalis, and Aggregatibacter actinomycetemcomitans inside the pocket was reduced significantly throughout the whole examination time. Greater pocket depth reductions were observed in all groups. There was a slight higher reduction of pocket depth in the lased group after six months. These results support the thesis that Er,Cr:YSGG laser supported periodontal treatment leads to a significant reduction of periopathogenes and thereby helps the maintenance of periodontal health.

Lasing in a nematic liquid crystal cell with an interdigitated electrode system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shtykov, N M; Palto, S P; Umanskii, B A

2015-04-30

Waveguide lasing in a layer of a dye-doped nematic liquid crystal has been observed. The liquid-crystal layer was sandwiched between a quartz substrate and a glass cover plate on whose surface was deposited an interdigitated electrode system. This system had a period of 3.75 μm and played a dual role, namely, it created a spatial periodicity of the waveguide medium refractive index (thus creating distributed feedback) and served as a diffraction grating coupling out a part of waveguide radiation into the glass cover plate. The distributed feedback ensured lasing in the 18th diffraction order for the TE modes and inmore » the 19th order for the TM modes of the waveguide. The generated radiation was observed at the exit from the glass plate end face at the angles to the waveguide plane of 33.1 ± 1.5° for TM modes and 21.8 ± 1.8° for TE modes. The intensity and position of the TE emission line showed no regular dependence on the voltage on the electrodes. In the case of TM radiation, an increase in the voltage led to a short-wavelength shift of the laser line and to a decrease in its intensity. (lasers)« less

Stimulated Axion Decay in Superradiant Clouds around Primordial Black Holes

NASA Astrophysics Data System (ADS)

Rosa, João G.; Kephart, Thomas W.

2018-06-01

The superradiant instability can lead to the generation of extremely dense axion clouds around rotating black holes. We show that, despite the long lifetime of the QCD axion with respect to spontaneous decay into photon pairs, stimulated decay becomes significant above a minimum axion density and leads to extremely bright lasers. The lasing threshold can be attained for axion masses μ ≳10-8 eV , which implies superradiant instabilities around spinning primordial black holes with mass ≲0.01 M⊙. Although the latter are expected to be nonrotating at formation, a population of spinning black holes may result from subsequent mergers. We further show that lasing can be quenched by Schwinger pair production, which produces a critical electron-positron plasma within the axion cloud. Lasing can nevertheless restart once annihilation lowers the plasma density sufficiently, resulting in multiple laser bursts that repeat until the black hole spins down sufficiently to quench the superradiant instability. In particular, axions with a mass ˜10-5 eV and primordial black holes with mass ˜1024 kg , which may account for all the dark matter in the Universe, lead to millisecond bursts in the GHz radio-frequency range, with peak luminosities ˜1042 erg /s , suggesting a possible link to the observed fast radio bursts.

Blood pressure, left ventricular geometry, and systolic function in children exposed to inorganic arsenic.

PubMed

Osorio-Yáñez, Citlalli; Ayllon-Vergara, Julio C; Arreola-Mendoza, Laura; Aguilar-Madrid, Guadalupe; Hernández-Castellanos, Erika; Sánchez-Peña, Luz C; Del Razo, Luz M

2015-06-01

Inorganic arsenic (iAs) is a ubiquitous element present in the groundwater worldwide. Cardiovascular effects related to iAs exposure have been studied extensively in adult populations. Few epidemiological studies have been focused on iAs exposure-related cardiovascular disease in children. In this study we investigated the association between iAs exposure, blood pressure (BP), and functional and anatomical echocardiographic parameters in children. A cross-sectional study of 161 children between 3 and 8 years was conducted in Central Mexico. The total concentration of arsenic (As) species in urine (U-tAs) was determined by hydride generation-cryotrapping-atomic absorption spectrometry and lifetime iAs exposure was estimated by multiplying As concentrations measured in drinking water by the duration of water consumption in years (LAsE). BP was measured by standard protocols, and M-mode echocardiographic parameters were determined by ultrasonography. U-tAs concentration and LAsE were significantly associated with diastolic (DBP) and systolic blood pressure (SBP) in multivariable linear regression models: DBP and SBP were 0.013 (95% CI: 0.002, 0.024) and 0.021 (95% CI: 0.004, 0.037) mmHg higher in association with each 1-ng/mL increase in U-tAs (p < 0.025), respectively. Left ventricular mass (LVM) was significantly associated with LAsE [5.5 g higher (95% CI: 0.65, 10.26) in children with LAsE > 620 compared with < 382 μg/L-year; p = 0.03] in an adjusted multivariable model. The systolic function parameters left ventricular ejection fraction (EF) and shortening fraction were 3.67% (95% CI: -7.14, -0.20) and 3.41% (95% CI: -6.44, -0.37) lower, respectively, in children with U-tAs > 70 ng/mL compared with < 35 ng/mL. Early-life exposure to iAs was significantly associated with higher BP and LVM and with lower EF in our study population of Mexican children.

Diffractive Combiner of Single-Mode Pump Laser-Diode Beams

NASA Technical Reports Server (NTRS)

Liu, Duncan; Wilson, Daniel; Qiu, Yueming; Forouhar, Siamak

2007-01-01

An optical beam combiner now under development would make it possible to use the outputs of multiple single-mode laser diodes to pump a neodymium: yttrium aluminum garnet (Nd:YAG) nonplanar ring oscillator (NPRO) laser while ensuring that the laser operates at only a single desired frequency. Heretofore, an Nd:YAG NPRO like the present one has been pumped by a single multimode laser-diode beam delivered via an optical fiber. It would be desirable to use multiple pump laser diodes to increase reliability beyond that obtainable from a single pump laser diode. However, as explained below, simplistically coupling multiple multimode laser-diode beams through a fiber-optic combiner would entail a significant reduction in coupling efficiency, and lasing would occur at one or more other frequencies in addition to the single desired frequency. Figure 1 schematically illustrates the principle of operation of a laser-diode-pumped Nd:YAG NPRO. The laser beam path is confined in a Nd:YAG crystal by means of total internal reflections on the three back facets and a partial-reflection coating on the front facet. The wavelength of the pump beam - 808 nm - is the wavelength most strongly absorbed by the Nd:YAG crystal. The crystal can lase at a wavelength of either 1,064 nm or 1,319 nm - which one depending on the optical coating on the front facet. A thermal lens effect induced by the pump beam enables stable lasing in the lowest-order transverse electromagnetic mode (the TEM00 mode). The frequency of this laser is very stable because of the mechanical stability of the laser crystal and the unidirectional nature of the lasing. The unidirectionality is a result of the combined effects of (1) a Faraday rotation induced by an externally applied magnetic field and (2) polarization associated with non-normal incidence and reflection on the front facet.

Comparing laser induced plasmas formed in diode and excimer pumped alkali lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Markosyan, Aram H.

Here, lasing on the D 1 transition (6 2P 1/2 → 6 2S 1/2) of cesium can be reached in both diode and excimer pumped alkali lasers. The first uses D 2 transition (6 2S 1/2 → 6 2P 3/2) for pumping, whereas the second is pumped by photoexcitation of ground state Cs-Ar collisional pairs and subsequent dissociation of diatomic, electronically-excited CsAr molecules (excimers). Despite lasing on the same D 1 transition, differences in pumping schemes enables chemical pathways and characteristic timescales unique for each system. We investigate unavoidable plasma formation during operation of both systems side by side inmore » Ar/C 2H 6/Cs.« less

Spectral singularity in composite systems and simulation of a resonant lasing cavity

NASA Astrophysics Data System (ADS)

Zhang, X. Z.; Li, G. R.; Song, Z.

2017-10-01

We investigate herein the existence of spectral singularities (SSs) in composite systems that consist of two separate scattering centers A and B embedded in one-dimensional free space, with at least one scattering center being non-Hermitian. We show that such composite systems have an SS at kc if the reflection amplitudes rA≤ft(kc\\right) and rB≤ft(kc\\right) of the two scattering centers satisfy the condition rR A≤ft(kc\\right) rLB≤ft(kc\\right) ei2kc≤ft(xB-xA\\right) =1 . We also extend the condition to the system with multi-scattering centers. As an application, we construct a simple system to simulate a resonant lasing cavity.

NONLINEAR AND FIBER OPTICS: Transient stimulated thermal scattering in a field of quasiplanar counterpropagating pump beams

NASA Astrophysics Data System (ADS)

Arutyunov, Yu A.; Bagan, A. A.; Gerasimov, V. B.; Golyanov, A. V.; Ogluzdin, Valerii E.; Sugrobov, V. A.; Khizhnyak, A. I.

1990-04-01

Theoretical analyses and experimental studies are made of transient stimulated thermal scattering in a thermal nonlinear medium subjected to a field of counterpropagating quasiplane waves. The equations for the counterpropagating four-beam interaction are solved analytically for pairwise counterpropagating scattered waves using the constant pump wave intensity approximation. The conditions for the occurrence of an absolute instability of the scattered waves are determined and the angular dependence of their increment is obtained; these results are in good agreement with experimental data. An investigation is reported of the dynamics of spiky lasing in a laser with resonators coupled by a dynamic hologram in which stimulated thermal scattering is a source of radiation initiating lasing in the system as a whole.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slipchenko, S. O., E-mail: serghpl@mail.ioffe.ru; Podoskin, A. A.; Pikhtin, N. A.

Threshold conditions for generation of a closed mode in the crystal of the Fabry-Perot semiconductor laser with a quantum-well active region are analyzed. It is found that main parameters affecting the closed mode lasing threshold for the chosen laser heterostructure are as follows: the optical loss in the passive region, the optical confinement factor of the closed mode in the gain region, and material gain detuning. The relations defining the threshold conditions for closed mode lasing in terms of optical and geometrical characteristics of the semiconductor laser are derived. It is shown that the threshold conditions can be satisfied atmore » a lower material gain in comparison with the Fabry-Perot cavity mode due to zero output loss for the closed mode.« less

Temperature characteristics of epitaxially grown InAs quantum dot micro-disk lasers on silicon for on-chip light sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wan, Yating; Li, Qiang; Lau, Kei May, E-mail: eekmlau@ust.hk

2016-07-04

Temperature characteristics of optically pumped micro-disk lasers (MDLs) incorporating InAs quantum dot active regions are investigated for on-chip light sources. The InAs quantum dot MDLs were grown on V-groove patterned (001) silicon, fully compatible with the prevailing complementary metal oxide-semiconductor technology. By combining the high-quality whispering gallery modes and 3D confinement of injected carriers in quantum dot micro-disk structures, we achieved lasing operation from 10 K up to room temperature under continuous optical pumping. Temperature dependences of the threshold, lasing wavelength, slope efficiency, and mode linewidth are examined. An excellent characteristic temperature T{sub o} of 105 K has been extracted.

Unidirectional, dual-comb lasing under multiple pulse formation mechanisms in a passively mode-locked fiber ring laser.

PubMed

Liu, Ya; Zhao, Xin; Hu, Guoqing; Li, Cui; Zhao, Bofeng; Zheng, Zheng

2016-09-19

Dual-comb lasers simultaneously generating asynchronous ultrashort pulses could be an intriguing alternative to the current dual-laser comb source. When generated through a common light path, the low common-mode noises and good coherence between the pulse trains could be realized. Here we demonstrate the completely common-path, unidirectional dual-comb lasing using a carbon nanotube saturable absorber with additional pulse narrowing and broadening mechanisms. The interactions between multiple soliton formation mechanisms result in bifurcation into unusual two-pulse states with pulses of four-fold bandwidth difference and tens-of-Hz repetition rate difference. Coherence between the pulses is verified by the asynchronous cross-sampling and dual-comb spectroscopy measurements.

Time-resolved measurements of the angular distribution of lasing at 23.6 nm in Ne-like germanium

NASA Astrophysics Data System (ADS)

Kodama, R.; Neely, D.; Dwivedi, L.; Key, M. H.; Krishnan, J.; Lewis, C. L. S.; O'Neill, D.; Norreys, P.; Pert, G. J.; Ramsden, S. A.; Tallents, G. J.; Uhomoibhi, J.; Zhang, J.

1992-06-01

The time dependence of the angular distribution of soft X-ray lasing at 23.6 nm in Ne-like germanium has been measured using a streak camera. Slabs of germanium have been irradiated over ≈ 22 mm length × 100 μm width with three line focussed beams of the SERC Rutherford Appleton Laboratory VULCAN laser at 1.06 μm wavelength. The laser beam sweeps in time towards the target surface plane and the divergence broadens with time. The change of the peak intensity pointing and the broadening of the profile with time are consistent with expectations of the time dependence of refraction and divergence due to density gradients in the plasma.

Large diameter lasing tube cooling arrangement

DOEpatents

Hall, Jerome P [Livermore, CA; Alger, Terry W [Tracy, CA; Anderson, Andrew T [Livermore, CA; Arnold, Phillip A [Livermore, CA

2004-05-18

A cooling structure (16) for use inside a ceramic cylindrical tube (11) of a metal vapor laser (10) to cool the plasma in the tube (11), the cooling structure (16) comprising a plurality of circular metal members (17, 31) and mounting members (18, 34) that position the metal members (17, 31) coaxially in the tube (11) to form an annular lasing volume, with the metal members (17, 31) being axially spaced from each other along the length of the tube (11) to prevent the metal members from shorting out the current flow through the plasma in the tube (11) and to provide spaces through which the heat from localized hot spots in the plasma may radiate to the other side of the tube (11).

Large Diameter Lasing Tube Cooling Arrangement

DOEpatents

Hall, Jerome P.; Alger, Terry W.; Anderson, Andrew T.; Arnold, Philip A.

2004-05-18

A cooling structure (16) for use inside a ceramic cylindrical tube (11) of a metal vapor laser (10) to cool the plasma in the tube (11), the cooling structure (16) comprising a plurality of circular metal members (17,31) and mounting members (18, 34) that position the metal members (17,31) coaxially in the tube (11) to form an annular lasing volume, with the metal members (17, 31) being axially spaced from each other along the length of the tube (11) to prevent the metal members from shorting out the current flow through the plasma in the tube (11) and to provide spaces through which the heat from localized hot spots in the plasma may radiate to the other side of the tube (11).

Lateral mode control in edge-emitting lasers with modified mirrors

NASA Astrophysics Data System (ADS)

Payusov, A.; Serin, A.; Mukhin, I.; Shernyakov, Y.; Zadiranov, Y.; Maximov, M.; Gordeev, N.

2017-11-01

We present a study on lateral mode control in edge-emitting lasers with profiled mirror reflectivity. The object was to eliminate high-order lateral modes in conventional ridge-waveguide InAs/InGaAs QD (quantum dot) lasers with the stripe width of 10 μm. We have used a FIB (focused ion beam) technique to selectively etch windows in the AR (anti-reflection) facet coatings in order to introduce extra mirror losses for the high order modes. This approach allowed us to eliminate the first-order mode lasing without deterioration of the laser parameters. We suppose that further optimisation of the laser heterostructure and window designs may lead to a pure lateral single-mode lasing in the broadened ridge waveguides.

Comparing laser induced plasmas formed in diode and excimer pumped alkali lasers

DOE PAGES

Markosyan, Aram H.

2018-01-05

Here, lasing on the D 1 transition (6 2P 1/2 → 6 2S 1/2) of cesium can be reached in both diode and excimer pumped alkali lasers. The first uses D 2 transition (6 2S 1/2 → 6 2P 3/2) for pumping, whereas the second is pumped by photoexcitation of ground state Cs-Ar collisional pairs and subsequent dissociation of diatomic, electronically-excited CsAr molecules (excimers). Despite lasing on the same D 1 transition, differences in pumping schemes enables chemical pathways and characteristic timescales unique for each system. We investigate unavoidable plasma formation during operation of both systems side by side inmore » Ar/C 2H 6/Cs.« less

Algorithm for measuring the internal quantum efficiency of individual injection lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sommers, H.S. Jr.

1978-05-01

A new algorithm permits determination of the internal quantum efficiency eta/sub i/ of individual lasers. Above threshold, the current is partitioned into a ''coherent'' component driving the lasing modes and the ''noncoherent'' remainder. Below threshold the current is known to grow as exp(qV/n/sub 0/KT); the algorithm proposes that extrapolation of this equation into the lasing region measures the noncoherent remainder, enabling deduction of the coherent component and of its current derivative eta/sub i/. Measurements on five (AlGa)As double-heterojunction lasers cut from one wafer demonstrate the power of the new method. Comparison with band calculations of Stern shows that n/sub 0/more » originates in carrier degeneracy.« less

Fusion pumped laser

DOEpatents

Pappas, D.S.

1987-07-31

The apparatus of this invention may comprise a system for generating laser radiation from a high-energy neutron source. The neutron source is a tokamak fusion reactor generating a long pulse of high-energy neutrons and having a temperature and magnetic field effective to generate a neutron flux of at least 10/sup 15/ neutrons/cm/sup 2//center dot/s. Conversion means are provided adjacent the fusion reactor at a location operable for converting the high-energy neutrons to an energy source with an intensity and energy effective to excite a preselected lasing medium. A lasing medium is spaced about and responsive to the energy source to generate a population inversion effective to support laser oscillations for generating output radiation. 2 figs., 2 tabs.

Fusion pumped laser

DOEpatents

Pappas, Daniel S.

1989-01-01

Apparatus is provided for generating energy in the form of laser radiation. A tokamak fusion reactor is provided for generating a long, or continuous, pulse of high-energy neutrons. The tokamak design provides a temperature and a magnetic field which is effective to generate a neutron flux of at least 10.sup.15 neutrons/cm.sup.2.s. A conversion medium receives neutrons from the tokamak and converts the high-energy neutrons to an energy source with an intensity and an energy effective to excite a preselected lasing medium. The energy source typically comprises fission fragments, alpha particles, and radiation from a fission event. A lasing medium is provided which is responsive to the energy source to generate a population inversion which is effective to support laser oscillations for generating output radiation.

Comparing laser induced plasmas formed in diode and excimer pumped alkali lasers.

PubMed

Markosyan, Aram H

2018-01-08

Lasing on the D 1 transition (6 2 P 1/2 → 6 2 S 1/2 ) of cesium can be reached in both diode and excimer pumped alkali lasers. The first uses D 2 transition (6 2 S 1/2 → 6 2 P 3/2 ) for pumping, whereas the second is pumped by photoexcitation of ground state Cs-Ar collisional pairs and subsequent dissociation of diatomic, electronically-excited CsAr molecules (excimers). Despite lasing on the same D 1 transition, differences in pumping schemes enables chemical pathways and characteristic timescales unique for each system. We investigate unavoidable plasma formation during operation of both systems side by side in Ar/C 2 H 6 /Cs.

A High-Average-Power Free Electron Laser for Microfabrication and Surface Applications

NASA Technical Reports Server (NTRS)

Dylla, H. F.; Benson, S.; Bisognano, J.; Bohn, C. L.; Cardman, L.; Engwall, D.; Fugitt, J.; Jordan, K.; Kehne, D.; Li, Z.;

Multi-exciton emission from solitary dopant states of carbon nanotubes.

PubMed

Ma, Xuedan; Hartmann, Nicolai F; Velizhanin, Kirill A; Baldwin, Jon K S; Adamska, Lyudmyla; Tretiak, Sergei; Doorn, Stephen K; Htoon, Han

2017-11-02

By separating the photons from slow and fast decays of single and multi-exciton states in a time gated 2 nd order photon correlation experiment, we show that solitary oxygen dopant states of single-walled carbon nanotubes (SWCNTs) allow emission of photon pairs with efficiencies as high as 44% of single exciton emission. Our pump dependent time resolved photoluminescence (PL) studies further reveal diffusion-limited exciton-exciton annihilation as the key process that limits the emission of multi-excitons at high pump fluences. We further postulate that creation of additional permanent exciton quenching sites occurring under intense laser irradiation leads to permanent PL quenching. With this work, we bring out multi-excitonic processes of solitary dopant states as a new area to be explored for potential applications in lasing and entangled photon generation.

High-speed observation of ZnO microspherical crystals produced by laser ablation (Conference Presentation)

NASA Astrophysics Data System (ADS)

Nakamura, Daisuke; Tasaki, Ryohei; Fujiwara, Yuki; Nagasaki, Fumiaki; Higashihata, Mitsuhiro; Ikenoue, Hiroshi; Okada, Tatsuo

2017-03-01

ZnO nano/microstructures have attracted much attention as building blocks for optoelectronic devices because of their high crystalline quality and unique structures. We have succeeded in synthesizing ZnO microspherical crystals by a simple atmospheric laser ablation method, and demonstrated ultraviolet whispering-gallery-mode lasing from the spheres. In the microsphere synthesis process, molten droplets formed into spherical shapes by surface tension, and crystalized during ejection from the ablation spot. In this study, we observed the generation of ZnO microspheres by high-speed camera. Now we are trying to control and manipulate the microspheres using a vortex beam.

Remembering the laser diode

NASA Astrophysics Data System (ADS)

2012-12-01

Fifty years ago, researchers at a handful of laboratories around the world were reporting lasing from the first semiconductor lasers. Our IT infrastructure today relies on their diligence and success.

High-order random Raman lasing in a PM fiber with ultimate efficiency and narrow bandwidth

PubMed Central

Babin, Sergey A.; Zlobina, Ekaterina A.; Kablukov, Sergey I.; Podivilov, Evgeniy V.

2016-01-01

Random Raman lasers attract now a great deal of attention as they operate in non-active turbid or transparent scattering media. In the last case, single mode fibers with feedback via Rayleigh backscattering generate a high-quality unidirectional laser beam. However, such fiber lasers have rather poor spectral and polarization properties, worsening with increasing power and Stokes order. Here we demonstrate a linearly-polarized cascaded random Raman lasing in a polarization-maintaining fiber. The quantum efficiency of converting the pump (1.05 μm) into the output radiation is almost independent of the Stokes order, amounting to 79%, 83%, and 77% for the 1st (1.11 μm), 2nd (1.17 μm) and 3rd (1.23 μm) order, respectively, at the polarization extinction ratio >22 dB for all orders. The laser bandwidth grows with increasing order, but it is almost independent of power in the 1–10 W range, amounting to ~1, ~2 and ~3 nm for orders 1–3, respectively. So, the random Raman laser exhibits no degradation of output characteristics with increasing Stokes order. A theory adequately describing the unique laser features has been developed. Thus, a full picture of the cascaded random Raman lasing in fibers is shown. PMID:26940082

Research on tunable multiwavelength fiber lasers with two-section birefringence fibers and a nonlinear optical loop

NASA Astrophysics Data System (ADS)

Chen, Jiao; Tong, Zhengrong; Zhang, Weihua; Xue, Lifang; Pan, Honggang

2018-05-01

Two types of tunable multiwavelength fiber lasers based on two-section polarization maintaining fibers (PMFs) cascaded/in parallel and nonlinear optical loop are proposed and experimentally demonstrated. Two-section cascaded PMFs and two polarization controllers (PCs) form the two-stage Lyot filter, which can generate comb spectrum to achieve multiwavelength output. When two sections of PMFs are in parallel, PCs in two paths are adjusted to change the beam’s polarization to suppress the light of one branch, and then the light of the other branch passes through the cavity. Additionally, a nonlinear optical loop acts as an intensity-dependent component, which can suppress the mode competition to maintain a stable output of multiwavelength lasing. The nonlinear optical loop is made by a 3 dB coupler, a PC3, and a 200 m high nonlinear fiber. Two types of tunable multiwavelength fiber lasers can achieve tuning of the channel space and the number of lasing wavelengths by adjusting PC1 and PC2. The channel space of the multiwavelengh laser can be tuned at nearly 0.4, 0.68, and 0.92 nm. Meanwhile, the spectral range of multiwavelength lasing can be controlled by PC3 in the nonlinear optical loop, and the tuning range of two multiwavelength lasers is about 2.28 and 1.45 nm, respectively.

[Influence AquaLase at corneal endothelial cells].

PubMed

Jirásková, N; Rozsíval, P; Ludvíková, M; Burova, M; Nekolová, J

2009-07-01

To assess the effect of the cleaning of the posterior capsule using pulses of balanced salt solution (BSS) on the corneal endothelial cells. This pilot study involves 43 patients with bilateral cataracts having lens removal using torsional phacoemulsification (Ozil, Infiniti, Alcon) and bimanul irrigation/aspiration (I/A). Posterior capsule of the right eye of each patient was cleaned using pulses of BSS (AquaLase, Infiniti, Alcon). Surgery was performed by one of 2 surgeons (NJ, PR), both eyes of each patient was operated on by the same surgeon. Best corrected visual acuity (BCVA), endotelial cell count and pachymetry were evaluated pre- and postoperatively as well as occurence af peri- and postoperative complications. Preoperative mean pachymetry (P) was 566 +/- 45 microm in the right eye (RE) and 562 +/- 42 microm in the left eye (LE), mean endotelial cell count (ECC) 2541 +/- 317 cells/mm2 (RE) and 2567 +/- 311 cells/mm2 (LE). Three months after surgery P was 557 +/- 43 microm (RE) and 558 +/- 45 microm (LE) and ECC 2368 +/- 416 cells/mm2 (RE) and 2396 +/- 417 cells/mm2 (LE). There was no statistical difference in postoperative changes of both corneal parameters between right and left eyes. Best corrected visual acuity improved in all eyes and no peri-or postoperative complications occured. Cleaning of the posterior capsule using AquaLase is safe for corneal endothelial cells.

A Faraday laser lasing on Rb 1529 nm transition.

PubMed

Chang, Pengyuan; Peng, Huanfa; Zhang, Shengnan; Chen, Zhangyuan; Luo, Bin; Chen, Jingbiao; Guo, Hong

2017-08-21

We present the design and performance characterization of a Faraday laser directly lasing on the Rb 1529 nm transition (Rb, 5P 3/2  - 4D 5/2 ) with high stability, narrow spectral linewidth and low cost. This system does not need an additional frequency-stabilized pump laser as a prerequisite to preparing Rb atom from 5S to 5P excited state. Just by using a performance-improved electrodeless discharge lamp-based excited-state Faraday anomalous dispersion optical filter (LESFADOF), we realized a heterogeneously Faraday laser with the frequency corresponding to atomic transition, working stably over a range of laser diode (LD) current from 85 mA to 171 mA and the LD temperature from 11 °C to 32 °C, as well as the 24-hour long-term frequency fluctuation range of no more than 600 MHz. Both the laser linewidth and relative intensity noisy (RIN) are measured. The Faraday laser lasing on Rb 1529 nm transition (telecom C-band) can be applied to further research on metrology, microwave photonics and optical communication systems. Besides, since the transitions correspongding to the populated excited-states of alkali atoms within lamp are extraordinarily rich, this scheme can increase the flexibility for choosing proper wavelengths for Faraday laser and greatly expand the coverage of wavelength corresponding to atomic transmission for laser frequency stabilization.

NONLINEAR OPTICAL PHENOMENA Intracavity SRS conversion in diode-pumpedmultifunctional Nd3+:SrMoO4 laser crystal

NASA Astrophysics Data System (ADS)

Basiev, Tasoltan T.; Smetanin, Sergei N.; Fedin, Aleksandr V.; Shurygin, Anton S.

2010-10-01

Lasing of a miniature all-solid-state SRS laser based on a Nd3+:SrMoO4 crystal with a LiF:F2--passive Q-switch is studied. The dependences of the laser and SRS self-conversion parameters on the initial transmission of the passive Q-switch are studied experimentally and theoretically. Simulation of the lasing kinetics has shown the possibility of nonlinear cavity dumping upon highly efficient SRS self-conversion of laser radiation. An increase in the active medium length from 1 to 3mm resulted in an increase in the energy of the output 1.17-μm SRS radiation from 20 μJ to record-high 60 μJ at the absorbed multimode diode pump energy of 3.7 mJ.

A linear cavity multiwavelength fiber laser with adjustable lasing line number for fixed spectral regions

NASA Astrophysics Data System (ADS)

Tian, J. J.; Yao, Y.

2011-03-01

We report an experimental demonstration of muliwavelength erbium-doped fiber laser with adjustable wavelength number based on a power-symmetric nonlinear optical loop mirror (NOLM) in a linear cavity. The intensity-dependent loss (IDL) induced by the NOLM is used to suppress the mode competition and realize the stable multiwavelength oscillation. The controlling of the wavelength number is achieved by adjusting the strength of IDL, which is dependent on the pump power. As the pump power increases from 40 to 408 mW, 1-7 lasing line(s) at fixed wavelength around 1601 nm are obtained. The output power stability is also investigated. The most power fluctuation of single wavelength is less than 0.9 dB, when the wavelength number is increased from 1-7.

FY 1980 Report on Dye Laser Materials

DTIC Science & Technology

1981-02-01

C02H H Rh 19 H C2H 5 CH3 CO9H H i Rh6G H C2H 5 CH3 Co2 C2H5 H RhB C2H5 C2H!5 H CO,H H Rh3B C2A5 C2H5 H CO2CH 5 H Rh 101 RING- RING RING...Dye designations Ring SRh 101 Rh 101 - Diethyl SRh B Rh B Rhb 3B Mono ethyl (methyl) -- Rh 19 (116) Rh 6G Unsubstituted -- Rh 110 Rh 123 Nominal Single...Broadband Lasing Wave-lengths of the Rhodamine Dyes. Lasing Wavelength, n Approximate Dye Conc. x 104 Range Midpoint Rh 110 1.0 567-577 572 2.0 Rh 123

Dynamics of short-pulse generation via spectral filtering from intensely excited gain-switched 1.55-μm distributed-feedback laser diodes.

PubMed

Chen, Shaoqiang; Yoshita, Masahiro; Sato, Aya; Ito, Takashi; Akiyama, Hidefumi; Yokoyama, Hiroyuki

2013-05-06

Picosecond-pulse-generation dynamics and pulse-width limiting factors via spectral filtering from intensely pulse-excited gain-switched 1.55-μm distributed-feedback laser diodes were studied. The spectral and temporal characteristics of the spectrally filtered pulses indicated that the short-wavelength component stems from the initial part of the gain-switched main pulse and has a nearly linear down-chirp of 5.2 ps/nm, whereas long-wavelength components include chirped pulse-lasing components and steady-state-lasing components. Rate-equation calculations with a model of linear change in refractive index with carrier density explained the major features of the experimental results. The analysis of the expected pulse widths with optimum spectral widths was also consistent with the experimental data.

Tunable double-clad ytterbium-doped fiber laser based on a double-pass Mach-Zehnder interferometer

NASA Astrophysics Data System (ADS)

Meng, Yichang; Zhang, Shumin; Wang, Xinzhan; Du, Juan; Li, Hongfei; Hao, Yanping; Li, Xingliang

2012-03-01

We have demonstrated an adjustable double-clad Yb 3+-doped fiber laser using a double-pass Mach-Zehnder interferometer. The laser is adjustable over a range of 40 nm from 1064 nm to 1104 nm. By adjusting the state of the polarization controller, which is placed in the double-pass Mach-Zehnder interferometer, we obtained central lasing wavelengths that can be accurately tuned with controllable spacing between different tunable wavelengths. The laser has a side mode suppression ratio of 42 dB, the 3 dB spectral width is less than 0.2 nm, and the slope efficiencies at 1068 nm, 1082 nm and 1098 nm are 23%, 32% and 26%, respectively. In addition, we have experimentally observed tunable multi-wavelengths lasing output.

Dopamine sensing and measurement using threshold and spectral measurements in random lasers.

PubMed

Wan Ismail, Wan Zakiah; Liu, Guozhen; Zhang, Kai; Goldys, Ewa M; Dawes, Judith M

2016-01-25

We developed a novel dopamine sensing and measurement technique based on aggregation of gold nanoparticles in random lasers. Dopamine combined with copper ions triggers the aggregation of gold nanoparticles and thus affects the performance of random lasers. Dopamine sensing can be achieved using four parameters which are sensitive to the presence of dopamine, that is emission peak shift, emission linewidth, signal-to-noise ratio (peak emission intensity / noise) and random lasing threshold. The dopamine is most sensitively detected by a change in the emission linewidth with a limit of detection of 1 × 10(-7) M, as well as by an increase in the lasing threshold. The dopamine concentration from 1 × 10(-7) M to 1 × 10(-2) M can be determined by calibrating with the laser threshold.

Random lasing from Rhodamine 6G doped ethanediol solution based on the cicada wing nanocones

NASA Astrophysics Data System (ADS)

Zhang, Hua; Feng, Guoying; Zhang, Hong; Yang, Chao; Yin, Jiajia; Dai, Shenyu; Zhou, Shouhuan

2016-06-01

Random lasing from Rhdomaine 6G (Rh6G) doped ethanediol solution based on the cicada wing nanostructures as scatterers has been demonstrated. The optical positive feedback of the random laser is provided by these nanocones on the cicada wing, where the scale of the nanocones and the distance between them is about 150 nm and 200 nm, respectively. Al-coated reflector has been introduced to reduce the loss of the pump energy from the bottom, and moreover lower the laser threshold, which is about 126.0 μJ/pulse. Due to the liquid gain medium, the lifetime of this random laser is longer than conventional random lasers. This random laser shows the potential applications in biological random laser and photonic devices.

Forward voltage short-pulse technique for measuring high power laser array junction temperature

NASA Technical Reports Server (NTRS)

Meadows, Byron L. (Inventor); Amzajerdian, Frazin (Inventor); Barnes, Bruce W. (Inventor); Baker, Nathaniel R. (Inventor)

2012-01-01

The present invention relates to a method of measuring the temperature of the P-N junction within the light-emitting region of a quasi-continuous-wave or pulsed semiconductor laser diode device. A series of relatively short and low current monitor pulses are applied to the laser diode in the period between the main drive current pulses necessary to cause the semiconductor to lase. At the sufficiently low current level of the monitor pulses, the laser diode device does not lase and behaves similar to an electronic diode. The voltage across the laser diode resulting from each of these low current monitor pulses is measured with a high degree of precision. The junction temperature is then determined from the measured junction voltage using their known linear relationship.

Fusion pumped light source

DOEpatents

Pappas, Daniel S.

1989-01-01

Apparatus is provided for generating energy in the form of light radiation. A fusion reactor is provided for generating a long, or continuous, pulse of high-energy neutrons. The neutron flux is coupled directly with the lasing medium. The lasing medium includes a first component selected from Group O of the periodic table of the elements and having a high inelastic scattering cross section. Gamma radiation from the inelastic scattering reactions interacts with the first component to excite the first component, which decays by photon emission at a first output wavelength. The first output wavelength may be shifted to a second output wavelength using a second liquid component responsive to the first output wavelength. The light outputs may be converted to a coherent laser output by incorporating conventional optics adjacent the laser medium.

Lasing in circuit quantum electrodynamics with strong noise

NASA Astrophysics Data System (ADS)

Marthaler, M.; Utsumi, Y.; Golubev, D. S.

2015-05-01

We study a model which can describe a superconducting single-electron transistor or a double quantum dot coupled to a transmission-line oscillator. In both cases the degree of freedom is given by a charged particle, which couples strongly to the electromagnetic environment or phonons. We consider the case where a lasing condition is established and study the dependence of the average photon number in the resonator on the spectral function of the electromagnetic environment. We focus on three important cases: a strongly coupled environment with a small cutoff frequency, a structured environment peaked at a specific frequency, and 1 /f noise. We find that the electromagnetic environment can have a substantial impact on the photon creation. Resonance peaks are in general broadened and additional resonances can appear.

Ultrastable light sources in the crossover from superradiance to lasing

NASA Astrophysics Data System (ADS)

Xu, Minghui; Tieri, David; Holland, Murray

2013-05-01

We theoretically investigate the crossover from steady-state superradiance to optical lasing. An exact solution of the quantum master equation is difficult to obtain due to the exponential scaling of the Hilbert space dimension with system size. However, since Lindblad operators in the master equation are invariant under SU(4) transformations, we are able to reduce the exponential scaling of the problem to cubic by expanding the density matrix in terms of an SU(4) basis. In this way, we obtain exact quantum solutions of the superradiance-laser crossover. We use this theory to investigate the potential for ultrastable lasers in the millihertz linewidth regime, and find the behavior of important observables, such as intensity, linewidth, spin-correlation, and entanglement. This work was supported by the DARPA QUASAR program and NSF.

Organic holographic polymer dispersed liquid crystal distributed feedback laser from different diffraction orders

NASA Astrophysics Data System (ADS)

Liu, Minghuan; Liu, Yonggang; Zhang, Guiyang; Peng, Zenghui; Li, Dayu; Ma, Ji; Xuan, Li

2016-11-01

Holographic polymer dispersed liquid crystal (HPDLC) based distributed feedback (DFB) lasers were prepared with poly (-methoxy-5-(2‧-ethyl-hexyloxy)-1,4-phenylene-vinylene) (MEH-PPV) film as the active medium layer. The HPDLC grating film was fabricated via holographic induced photopolymerization. The pure film spectra of MEH-PPV and the amplified spontaneous emission (ASE) spectrum were investigated. The laser device was single-longitudinal mode operation. The tunability of the HPDLC DFB laser was achieved by selecting different grating periods. The lasing performances were also characterized and compared from different diffraction orders. The lasing threshold increased with the diffraction order and the third order laser possessed the largest conversion efficiency in this device. The experimental results were in good agreement with the theoretical calculations.

Laser diodes using InAlGaAs multiple quantum wells intermixed to varying extent

NASA Astrophysics Data System (ADS)

Alahmadi, Yousef; LiKam Wa, Patrick

2018-02-01

Bandgap-modified InAlGaAs/InP multi-quantum well lasers have been demonstrated using an impurity-free disordering technique. Varying degrees of disordering are achieved by rapidly annealing silicon nitride-capped samples at temperatures ranging from 730°C to 830°C for 20 s. The lasing wavelength shift resulting from the intermixing, ranges between 28.2 nm and 147.2 nm. As the annealing temperature is increased, the lasing threshold currents of the fabricated waveguide lasers increase from 25mA to 45mA, while the slope efficiency decrease from 0.101 W/A to 0.068 W/A, compared to a threshold current of 27.8 mA and a slope efficiency of 0.121 W/A for an as-grown laser diode.

Optical pumping of the. nu. /sub 3/ +. nu. /sub 4/ band of the CF/sub 4/ molecule

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piltch, M.S.; Hinsley, R.; Eckhardt, R.

1979-01-01

The possible development of a room-temperature, 16 ..mu..m CF/sub 4/ laser optically pumped by 5 ..mu..m radiation from a frequency-doubled CO/sub 2/ laser was investigated. This laser would utilize pumping of the ..nu../sub 3/ + ..nu../sub 4/ band of CF/sub 4/ at 1916 cm/sup -1/ with subsequent lasing to ..nu../sub 3/ levels at 1283 cm/sup -1/ where there is essentially no thermally excited population. A spectrophone instrument was used to measure absorption cross sections of CF/sub 4/ at the second harmonic frequencies of 22 of the 10 ..mu..m CO/sub 2/ laser transitions. Lasing experiments to detect transitions at 16 ..mu..mmore » are described.« less

Circular-polarization-sensitive metamaterial based on triple-quantum-dot molecules.

PubMed

Kotetes, Panagiotis; Jin, Pei-Qing; Marthaler, Michael; Schön, Gerd

2014-12-05

We propose a new type of chiral metamaterial based on an ensemble of artificial molecules formed by three identical quantum dots in a triangular arrangement. A static magnetic field oriented perpendicular to the plane breaks mirror symmetry, rendering the molecules sensitive to the circular polarization of light. By varying the orientation and magnitude of the magnetic field one can control the polarization and frequency of the emission spectrum. We identify a threshold frequency Ω, above which we find strong birefringence. In addition, Kerr rotation and circular-polarized lasing action can be implemented. We investigate the single-molecule lasing properties for different energy-level arrangements and demonstrate the possibility of circular-polarization conversion. Finally, we analyze the effect of weak stray electric fields or deviations from the equilateral triangular geometry.

BeZnCdSe quantum-well ridge-waveguide laser diodes under low threshold room-temperature continuous-wave operation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Jijun; Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology; Akimoto, Ryoichi, E-mail: r-akimoto@aist.go.jp

2015-10-19

Low threshold current ridge-waveguide BeZnCdSe quantum-well laser diodes (LDs) have been developed by completely etching away the top p-type BeMgZnSe/ZnSe:N short-period superlattice cladding layer, which can suppress the leakage current that flows laterally outside of the electrode. The waveguide LDs are covered with a thick SiO{sub 2} layer and planarized with chemical-mechanical polishing and a reactive ion etching process. Room-temperature lasing under continuous-wave condition is achieved with the laser cavity formed by the cleaved waveguide facets coated with high-reflectivity dielectric films. For a 4 μm-wide green LD lasing around a wavelength of 535 nm, threshold current and voltage of 7.07 mA and 7.89 Vmore » are achieved for a cavity length of 300 μm, and the internal differential quantum efficiency, internal absorption loss, gain constant, and nominal transparency current density are estimated to be 27%, 4.09 cm{sup −1}, 29.92 (cm × μm)/kA and 6.35 kA/(cm{sup 2 }× μm), respectively. This compact device can realize a significantly improved performance with much lower threshold power consumption, which would benefit the potential application for ZnSe-based green LDs as light sources in full-color display and projector devices installed in consumer products such as pocket projectors.« less

Room temperature high circular dichroism ultraviolet lasing from planar spiral metal-GaN nanowire cavity (Conference Presentation)

NASA Astrophysics Data System (ADS)

Shih, Min-Hsiung

2016-09-01

Circularly polarized light and chiroptical effect have received considerable attention in advanced photonic and electronic technologies including optical spintronics, quantum-based optical information processing and communication, and high-efficiency liquid crystal display backlights. Moreover, the development of circularly polarized photon sources has played a major role in circular dichroism (CD) spectroscopy, which is important for analyses of optically active molecules, chiral synthesis in biology and chemistry, and ultrafast magnetization control. However, the conventional collocation of light-emitting devices and additional circular-polarization converters that produce circularly polarized beams makes the setup bulky and hardly compatible with nanophotonic devices in ultrasmall scales. In fact, the direct generation of circularly polarized photons may simplify the system integration, compact the setup, lower the cost of external components, and perhaps enhance the power efficiency. In this work, with the spiral-type metal-gallium nitride (GaN) nanowire cavity, we demonstrated an ultrasmall semiconductor laser capable of emitting circularly-polarized photons. The left- and right-hand spiral metal nanowire cavities with varied periods were designed at ultraviolet wavelengths to achieve the high quality factor circular dichroism metastructures. The dissymmetry factors characterizing the degrees of circular polarizations of the left- and right-hand chiral lasers were 1.4 and -1.6 (2 if perfectly circular polarized), respectively. The results show that the chiral cavities with only 5 spiral periods can achieve lasing signals with decently high degrees of circular polarizations.

Light amplification and lasing from dyes doped in DNA-complex thin films prepared by soaking method

NASA Astrophysics Data System (ADS)

Kawabe, Yutaka; Suzuki, Takemasa; Iisaka, You

2014-08-01

An alternative fabrication method for dye-doped DNA-surfactant complex films was developed and amplified spontaneous emission (ASE) and lasing under low energy optical pumping were demonstrated. In this new preparation technique, thin DNA-cethyltrimethylammonium (CTMA) complex films made by a spin coating method were stained with a hemicyanine dye by soaking them in acetone solution of the dye for one day. Molar ratio of the dye to DNA base pair for the final products was estimated to be 0.2, the value was much higher than those achieved via usual mixing method. ASE threshold value under pumping of a pulsed frequency-doubled YAG laser was about 0.3 mJ/cm2. Laser emission was also attained under the excitation with two interfering beams forming a dynamic grating of gain coefficient. Durability test indicated that 70% of their initial performance was maintained after 1 hour of continuous pumping. The technique was applied to water soluble dyes because the DNA complex was insoluble to water as well as acetone. We employed anionic Eosin Y dye, succeeding in sample formation and ASE emission. Different types of surfactants were also complexed with DNA, showing variation of emission peak wavelength. These results give a clue about the structure of the complex or interaction modes between DNA and surfactants, strongly suggesting that dye molecules are not intercalated into nor bound to DNA double strand directly, but are incorporated in the complex system via ion-exchange process or aggregating with cationic surfactants.

Spectroscopic investigations of Nd3+ doped Lithium Lead Alumino Borate glasses for 1.06 μm laser applications

NASA Astrophysics Data System (ADS)

Deopa, Nisha; Rao, A. S.; Gupta, Mohini; Vijaya Prakash, G.

2018-01-01

Neodymium doped lithium lead alumino borate glasses were synthesized with the molar composition 10Li2Osbnd 10PbOsbnd (10-x) Al2O3sbnd 70B2O3sbnd x Nd2O3 (where, x = 0.1, 0.5, 1.0, 1.5, 2.0 and 2.5 mol %) via conventional melt quenching technique to understand their lasing potentialities using the absorption, emission and photoluminescence decay spectral measurements. The oscillator strengths measured from the absorption spectra were used to estimate the Judd-Ofelt intensity parameters using least square fitting procedure. The emission spectra recorded for the as-prepared glasses under investigation exhibit two emission transitions 4F3/2 → 4I11/2 (1063 nm) and 4F3/2 → 4I9/2 (1350 nm) for which radiative parameters have been evaluated. The emission intensity increases with increase in Nd3+ ion concentration up to 1 mol % and beyond concentration quenching took place. The decay profile shows single exponential nature for lower Nd3+ ion concentration and non-exponential for higher concentration. To elucidate the nature of energy transfer process, the non-exponential decay curves were well fitted to Inokuti-Hirayama model. The relatively higher values of emission cross-sections, branching ratios and quantum efficiency values obtained for 1.0 mol% of Nd3+ ions in LiPbAlB glass suggests it's aptness in generating lasing action at 1063 nm in NIR region.

Bleaching and enamel surface interactions resulting from the use of highly-concentrated bleaching gels.

PubMed

Grazioli, Guillermo; Valente, Lisia Lorea; Isolan, Cristina Pereira; Pinheiro, Helena Alves; Duarte, Camila Gonçalves; Münchow, Eliseu Aldrighi

2018-03-01

Tooth bleaching is considered a non-invasive treatment, although the use of highly-concentrated products may provoke increased surface roughness and enamel demineralization, as well as postoperative sensitivity. Thus, the aim of this study was to investigate whether hydrogen peroxide (H 2 O 2 ) concentration would affect tooth bleaching effectiveness and the enamel surface properties. Enamel/dentin bovine specimens (6 × 4 mm) were immersed in coffee solution for 7 days and evaluated with a spectrophotometer (Easyshade; baseline), using the CIEL * a * b * color parameters. Hardness was measured using a hardness tester. The specimens were randomly assigned into four groups: one negative control, in which the specimens were not bleached, but they were irradiated with a laser-light source (Whitening Lase II, DMC Equipments); and three groups using distinct H 2 O 2 concentration, namely LP15% (15% Lase Peroxide Lite), LP25% (25% Lase Peroxide Sensy), and LP35% (35% Lase Peroxide Sensy), all products from DMC. The bleached specimens were also irradiated with the laser-light source. After bleaching, all specimens were evaluated using scanning electron microscopy (SEM). pH kinetics and rate was monitored during bleaching. The data were analyzed using ANOVA and Tukey's test (p < 0.05). All bleaching gels produced similar color change (p > 0.05). Concerning hardness, only the LP25% and LP35% significantly reduced hardness after bleaching; also, there was a progressive tendency for a greater percentage reduction in hardness with increased H 2 O 2 concentration of the gel (R 2  = 0.9973, p < 0.001). SEM showed that LP25% and LP35% produced an etching pattern on enamel with prism rods exposure. In conclusion, H 2 O 2 concentration above the 15% level does not increase bleaching effectiveness, and may increase the possibility for alteration of enamel hardness, surface morphology, and acidity of the medium. When using H 2 O 2 -based bleaching agents, dental practitioners should choose for less concentrated gels, e.g., around the 15% level. Copyright © 2017 Elsevier Ltd. All rights reserved.

Electrically tunable laser based on heliconical cholesteric (Conference Presentation)

NASA Astrophysics Data System (ADS)

Xiang, Jie; Varanytsia, Andrii; Minkowski, Fred; Paterson, Daniel A.; Imrie, Corrie T.; Lavrentovich, Oleg D.; Palffy-Muhoray, Peter

2016-09-01

STUDENT CONTRIBUTION: Cholesteric liquid crystals (CLC) self-assemble into a periodic supramolecular helical structure with properties of a one-dimensional photonic crystal. The CLCs doped with a fluorescent dye and optical pump enable a distributed feedback cavity and lasing [1]. Although lasing was observed in range of wavelength from near UV to near IR, a practical method of tuning of emission wavelength from a dye-doped CLC without structural destruction of a helix is not demonstrated yet. In this work, we demonstrate an electrically tunable dye-doped CLC laser based on the so-called oblique helicoidal, or heliconical, CLC state [2,3]. In this state, the molecules twist around the helicoidal axis, making an angle smaller than 90 degrees with the axis. Molecular tilt makes the heliconical structure different from the regular CLC (in which the molecules are perpendicular to the axis) and enable electric tunability [2,3]. An electric field applied parallel to the heliconical axis changes the pitch but does not realign the axis. When the field increases, the pitch decreases. As a result, the selective reflection band and a lasing wavelength move towards shorter wavelength. Using heliconical CLC and two laser dyes DCM and LD688, we demonstrate effective tuning of the laser emission wavelength from 574 nm to 722 nm. With appropriate laser dyes, the spectrum can be extended from near UV to near IR. Efficient electric tuning in the broad spectral range and small size of the heliconical cholesteric lasers makes them potentially useful for optical and biomedical applications. [1] P. Palffy-Muhoay, W.Y. Cao, M. Moreira, B. Taheri, A. Munoz, Photonics and lasing in liquid crystal [2] J. Xiang, S.V. Shiyanovskii, C.T. Imrie, O.D. Lavrentovich, Electrooptic Response of Chiral Nematic Liquid Crystals with Oblique Helicoidal Director, Phys Rev Lett, 112 (2014) 217801. [3] J. Xiang, Y.N. Li, Q. Li, D.A. Paterson, J.M.D. Storey, C.T. Imrie, O.D. Lavrentovich, Electrically Tunable Selective Reflection of Light from Ultraviolet to Visible and Infrared by Heliconical Cholesterics, Adv Mater, 27 (2015) 3014-3018.

Spectroscopy and lasing of Tm:SrMoO4 crystal near 1.5, 1.9, and 2.3-μm under 793-nm excitation

NASA Astrophysics Data System (ADS)

Šulc, Jan; Švejkar, Richard; Němec, Michal; Doroshenko, Maxim E.; Jelínková, Helena; Ivleva, Liudmila I.; Dunaeva, Elizaveta E.

2018-02-01

The spectroscopy properties and lasing of diode pumped Tm-doped strontium molybdate SrMoO4 single crystal were investigated at room temperature. The Tm:SrMoO4 crystal was grown by modified Stepanov method (2 wt.% of TmNbO4 in the melt). The tested Tm:SrMoO4 sample was cut from the grown crystal boule perpendicularly to growth direction 100. For spectroscopy and laser experiments 4.2mm thick plane-parallel face-polished plate (without AR coatings) was used. A fiber-coupled laser diode operating at wavelength 793nm was used for longitudinal Tm:SrMoO4 pumping which corresponds to 3H4 level excitation. Fluorescence spectra measurement showed strong emission in vicinity of 1.8 μm (3F4 -> 3H6 transition), and also significant emission close to wavelengths 1.45 μm (3H4 -> 3F4 transition) and 2.3 μm (3H4 -> 3H5 transition). The lasing was successfully reached for all these three transitions and output characteristics were measured. The pumping laser diode was operating in the pulsed regime with a low duty cycle. The 145mm long semi-hemispherical laser resonator consisted of flat pumping mirror (HT @ 0.79 μm) and curved (r = 150mm) output coupler. For each lasing transition the particular set of resonator mirrors was used to reach high reflexivity of pumping mirror and output coupler transmission 0.5% at laser operation wavelength. The obtained laser emission wavelengths were 1.95 μm, 1.45 & 1.49 μm, and 2.30 μm. In spite of low laser slope efficiency in respect to absorbed pumping power (0.45% for 3H4 -> 3F4 transition, 0.50% for 3F4 -> 3H6 transition and 0.83% for 3H4 -> 3H5 transition), results obtained are promising for further development of diode-pumped laser at 2.3 μm spectral region.

Computational modelling of Er(3+): Garnet laser materials

NASA Technical Reports Server (NTRS)

Spangler, Lee H.

1994-01-01

The Er(3+) ion has attracted a lot of interest for four reasons: (1) Its (4)I(sub 13/2) yields (4)I(sub 15/2) transition lases in the eyesafe region near 1.5 micron; (2) the (4)I(sub 13/2) transition lases near 2.8 micron, an important wavelength for surgical purposes; (3) it displays surprisingly efficient upconversion with lasing observed at 1.7, 1.2, 0.85, 0.56, 0.55, and 0.47 micron following 1.5 micron pumping; and (4) it has absorption bands at 0.96 and 0.81 micron and thus can be diode pumped. However, properties desirable for upconversion reduce the efficiency of 1.5 and 3 micron laser operation and vice versa. Since all of the processes are influenced by the host via the crystal field induced stark splittings in the Er levels, this project undertook modelling of the host influence on the Er lasinng behavior. While growth and measurement of all ten Er(3+) doped garnets is the surest way of identifying hosts which maximize upconversion (or conversly, 1.5 and 3 micron performance), it is also expensive - costing approximately $10,000/material or approximately $100,000 for the materials computationally investigated here. The calculations were performed using a quantum mechanical point charge model developed by Clyde Morrison at Harry Diamond Laboratories. The programs were used to fit the Er:YAG experimental energy levels so that the crystal field parameters, B(sub nm) could be extracted. From these radial factors, rho (sub n) were determined for Er(3+) in garnets. These, in combination with crystal field components, Anm, available from X-ray data, were used to predict energy levels for Er in the other nine garnet hosts. The levels in Er:YAG were fit with an rms error of 12.2/cm over a 22,000/cm range. Predicted levels for two other garnets for which literature values were available had rms errors of less than 17/cm , showing the calculations to be reliable. Based on resonances between pairs of calculated stark levels, the model predicts GSGG as the best host for 1.5 micron laser operation, GSGG or YSAG as the best host for a 2.8 micron operation, and LuGG as the best host for an upconversion material.

LASE

Atmospheric Science Data Center

2017-03-16

... Absorption Lidar (DIAL) system developed to measure water vapor, aerosol, and cloud profiles. These measurements can be used in ... heat flux, the water vapor component of the hydrologic cycle, and atmospheric transport using water vapor as a tracer of atmospheric ...

Vertical-Cavity Surface-Emitting 1.55-μm Lasers Fabricated by Fusion

NASA Astrophysics Data System (ADS)

Babichev, A. V.; Karachinskii, L. Ya.; Novikov, I. I.; Gladyshev, A. G.; Blokhin, S. A.; Mikhailov, S.; Iakovlev, V.; Sirbu, A.; Stepniak, G.; Chorchos, L.; Turkiewicz, J. P.; Voropaev, K. O.; Ionov, A. S.; Agustin, M.; Ledentsov, N. N.; Egorov, A. Yu.

2018-01-01

The results of studies on fabrication of vertical-cavity surface-emitting 1.55-μm lasers by fusing AlGaAs/GaAs distributed-Bragg-reflector wafers and an active region based on thin In0.74Ga0.26 As quantum wells grown by molecular-beam epitaxy are presented. Lasers with a current aperture diameter of 8 μm exhibit continuous lasing with a threshold current below 1.5 mA, an output optical power of 6 mW, and an efficiency of approximately 22%. Single-mode lasing with a side-mode suppression ratio of 40-45 dB is observed in the entire operating current range. The effective modulation frequency of these lasers is as high as 9 GHz and is limited by the low parasitic cutoff frequency and self-heating.