Continuous-wave Oscillator Research Articles

High-power CW oscillation of 1.3-µm wavelength InP-based photonic-crystal surface-emitting lasers.

We demonstrate high-power continuous-wave (CW) lasing oscillation of 1.3-µm wavelength InP-based photonic-crystal surface-emitting lasers (PCSELs). Single-mode operation with an output power of over 100 mW, a side-mode suppression ratio (SMSR) of over 50 dB, and a narrow single-lobe beam with a divergence angle of below 1.2° are successfully achieved by using a double-lattice photonic crystal structure consisting of high-aspect-ratio deep air holes. The double lattice is designed to enhance both the in-plane optical feedback and the surface radiation effects in the photonic crystal. The coupling coefficients for 180 ∘, +90 ∘, and -90 ∘ diffractions are estimated from the measurements of the photonic band structure as κ1D = 417 cm-1, κ2D+ = 135 cm-1, and κ2D- = 65 cm-1, respectively. The stable single-mode, high-beam-quality operation is attributed to these large coupling coefficients introduced by the asymmetric double-lattice structure.

A Hybrid Self-Seeded Ti:sapphire Laser with a Pumping Scheme Based on Spectral Beam Combination of Continuous Wave Diode and Pulsed DPSS Lasers

A wide variety of applications require high peak laser intensity in conjunction with a narrow spectral linewidth. Typically, injection-locked amplifiers have been employed for this purpose, where a continuous wave oscillator is amplified in a secondary external resonant amplifier cavity using a pulsed pump laser. In contrast, here we demonstrate a setup that combines a CW Ti:sapphire oscillator and pulsed amplifier in a single optical cavity, resulting in a compact system. Dichroic beam combination of blue wavelength semiconductor diodes and the green wavelength of a Nd:YAG laser allowed the simultaneous excitation of the Ti:sapphire crystal by both continuous wave and pulsed pump sources. A linewidth of <2 MHz is achieved in continuous wave operation, while the linewidth increases to about 10 MHz in the combined CW+pulsed mode with a pulse duration of 73 ns. A peak pulse intensity of 0.2 kW is achieved, which should enable efficient single-pass second harmonic generation in a nonlinear crystal.

Optimizing output spectral linewidth of fiber laser utilizing phase-shifted long-period fiber grating

Suppressing nonlinear effects in fiber laser by special fiber gratings has attracted growing attentions. Currently, most researches mainly focus on suppressing stimulated Raman scattering. However, the mitigation of the nonlinear effects, such as self-phase modulation or four wave mixing, which broaden the main lobe of the output laser spectrum has not been paid attention. We report a novel method for universally and conveniently optimizing output spectral linewidth of fiber laser by applying phase-shifted long-period fiber grating (PS-LPFG). A detailed design philosophy and method of PS-LPFG was proposed. Further, a symmetrical PS-LPFG was fabricated to verify the feasibility of the method. The central wavelength of the grating’s passband was designed to match the signal light of a 1075 nm fiber laser. A 200 W continuous-wave oscillator was also established to evaluate the PS-LPFG’s performance. Experimental results demonstrate that the spectral broadening of the main lobe is clearly alleviated. The 30 dB linewidth of the evaluation system is narrowed approximately 32.9% by the PS-LPFG. The 0.03 dB insertion loss of the fabricated grating avoids the deterioration of the signal laser’s power. Furthermore, the 0.023 °C/W thermal slope of the grating allows for potential applications in higher power fiber lasers.

Multifrequency Radiation at the Kilowatt Power Level in a Continuous Helical Gyroresonance K-Band Backward Wave Oscillator with External Reflections

Multifrequency Radiation at the Kilowatt Power Level in a Continuous Helical Gyroresonance K-Band Backward Wave Oscillator with External Reflections

Raman silicon laser based on a nanocavity fabricated by photolithography

Fabricating silicon photonics devices by CMOS-compatible processes is important for applications. Here, we demonstrate a Raman silicon laser based on a heterostructure nanocavity that was fabricated by immersion photolithography using an argon fluoride excimer laser. The Raman laser confines the pump light and the Stokes Raman scattered light in two resonant modes of the nanocavity. By using the presented CMOS-compatible approach, sufficiently high quality-factors can be obtained for both modes. The sample whose frequency spacing of the two resonant modes closely matches the Raman shift of silicon, achieves continuous-wave oscillation with a lasing threshold of 1.8 µW at room temperature.

Semiconductor disk laser in bi-frequency operation by laser ablation micromachining of a laser mirror.

We present bi-frequency continuous wave oscillation in a semiconductor disk laser through direct writing of loss-inducing patterns onto an intra-cavity high reflector mirror. The laser is a Vertical External Cavity Surface Emitting Laser which is optically pumped by up to 1.1 W of 808 nm light from a fibre coupled multi-mode diode laser, and oscillates on two Hermite-Gaussian spatial modes simultaneously, achieving wavelength separations between 0.2 nm and 5 nm around 995 nm. We use a Digital Micromirror Device (DMD) enabled laser ablation system to define spatially specific loss regions on a laser mirror by machining away the Bragg layers from the mirror surface. The ablated pattern is comprised of two orthogonal lines with the centermost region undamaged, and is positioned in the laser cavity so as to interact with the lasing mode, thereby promoting the simultaneous oscillation of the fundamental and a higher order spatial mode. We demonstrate bi-frequency oscillation over a range of mask gap sizes and pump powers.

High Power Diamond Raman Lasers

Laser gain materials possessing high thermal conductivity and robust mechanical properties are key prerequisites for high power lasers. We show that diamond, when configured as a Raman laser, enables access to these and other extreme properties, providing an important new route to high power and high brightness beam generation. Recent achievements in pulsed and continuous wave oscillators, beam combining amplifiers, and single longitudinal mode oscillators are summarized, along with wavelength extension of these concepts through adaption to other pumps, use of Raman cascading, and intracavity harmonic generation. To date, diamond laser powers have attained 750 W with efficiency and beam quality so far unperturbed by nonlinear or thermally induced side-effects. Large factor brightness enhancement of low coherence inputs is demonstrated using multiple pump beams (via Raman beam combination) or highly multimode pumps for oscillator and amplifier configurations. Future directions for direct diode pumping, and for realizing extraordinary power and power density through reduced temperature operation and isotopically enriched diamond, are also discussed. Our results indicate that diamond is emerging as a generic high-power laser technology with advantages in terms of brightness (high average power and high beam quality) and wavelength range.

Self-Induced Faraday Instability Laser.

We predict the onset of self-induced parametric or Faraday instabilities in a laser, spontaneously caused by the presence of pump depletion, which leads to a periodic gain landscape for light propagating in the cavity. As a result of the instability, continuous wave oscillation becomes unstable even in the normal dispersion regime of the cavity, and a periodic train of pulses with ultrahigh repetition rate is generated. Application to the case of Raman fiber lasers is described, in good quantitative agreement between our conceptual analysis and numerical modeling.

Status and Prospects of High-Power Heterostructure Barrier Varactor Frequency Multipliers

There is a high demand for compact, room-temperature sources operating at millimeter-wave and terahertz (THz) frequencies for space instruments and terrestrial applications. This part of the electromagnetic spectrum is by far the least explored because of the difficulty of generating energy at these frequencies. Continuous-wave oscillators based on either electronics or photonics are limited in output power for fundamental reasons. Varistor and varactor frequency multipliers have shown outstanding performance in terms of output power, but further technical development will be essential to solve the lack of efficient and compact terahertz sources. In this paper, we present the status of heterostructure barrier varactor (HBV) diode frequency multipliers. The performance and prospects for THz applications in which HBV diode technology can offer advantages over conventional solutions are discussed. For instance, such a device can be easily scaled by increasing the number of barriers to produce and handle higher power. The inherent symmetry confines the power generation to odd harmonics, thereby simplifying the design of high-order frequency multipliers. For example, high-power triplers ( $\times 3$ ), quintuplers ( $\times 5$ ), nonlinear transmission lines (NLTLs) and grid multipliers utilizing HBV diodes are presented. Overall, HBV technology is a natural stepping stone from high-power microwave amplifiers to higher frequencies and can both simplify and improve the performance of terahertz sources.

Demonstration of a photonic crystal surface-emitting laser pumped Yb:YAG laser.

We developed a cryogenically cooled Yb:YAG continuous wave oscillator directly pumped with a photonic crystal surface-emitting laser (PCSEL). A high slope efficiency of 65.7% was obtained at an output power of 208 mW. The beam quality was close to the diffraction limit, with M2<1.2 in both directions. To the best of our knowledge, this is the first PCSEL pumped solid state laser to be developed.

Spectroscopy and tunable continuous-wave operation of single crystal around

Hexagonal single crystals of the solid solution are grown by the Bridgman – Stockbarger technique. We study their optical and photoluminescent characteristics and determine the temperature dependences of the photoluminescence kinetics within the range . The crystals possess a broad gain band in the range from 2 to and exhibit a weak quenching of luminescence with a quantum yield exceeding 80 % at room temperature. Tunable continuous-wave oscillation is demonstrated in the region of .

Dynamic characterization of intracavity losses in broadband quasi-three-level lasers.

We present a simple, fast and accurate technique to characterize intracavity losses in broadband quasi-three-level lasers based on spectroscopic gain analysis. The technique is based on spectral gain measurement and potentially can be used at any laser output power levels, thus allowing a dynamic optimization of laser performance. Successful experimental demonstration was carried out with a diode-pumped Yb:KGW continuous wave oscillator. A comparison with traditional Findlay-Clay analysis and numerical modeling was also made.

Mode locking with enhanced nonlinearity - a detailed study

We explore mode locked operation of a Ti:Sapphire laser with enhanced Kerr nonlinearity, where the threshold for pulsed operation can be continuously tuned down to the threshold for continuous-wave (CW) operation, and even below it. At the point of equality, even though a CW solution does not exist, pulsed oscillation can be realized directly from zero CW oscillation. We experimentally investigate the evolution of the mode locking mechanism towards this point and beyond it, and provide a qualitative theoretical model to explain the results.

Oscillation characteristics of electrically-pumped vertical external cavity surface emitting lasers

PDF HTML阅读 XML下载 导出引用 引用提醒 电泵浦垂直外腔面发射激光器振荡特性的理论分析及实验研究 DOI: 作者: 作者单位: 中国科学院长春光学精密机械与物理研究所,中国科学院长春光学精密机械与物理研究所,中国科学院长春光学精密机械与物理研究所 发光学及应用国家重点实验室,中国科学院长春光学精密机械与物理研究所 发光学及应用国家重点实验室,中国科学院长春光学精密机械与物理研究所 发光学及应用国家重点实验室,中国科学院长春光学精密机械与物理研究所 发光学及应用国家重点实验室,中国科学院长春光学精密机械与物理研究所 发光学及应用国家重点实验室,中国科学院长春光学精密机械与物理研究所 发光学及应用国家重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(61204056,61234004,11074247,51172225), 吉林省科技发展项目(201105025,20116011) Oscillation characteristics of electrically-pumped vertical external cavity surface emitting lasers Author: Affiliation: Changchun Institute of Optics,Fine Mechanics and Physics,Chinese Academy of Sciences,Changchun Institute of Optics,Fine Mechanics and Physics,Chinese Academy of Sciences,State Key Laboratory of Luminescence and Applications,Changchun Institute of Optics,Fine Mechanics and Physics,Chinese Academy of Sciences,State Key Laboratory of Luminescence and Applications,Changchun Institute of Optics,Fine Mechanics and Physics,Chinese Academy of Sciences,State Key Laboratory of Luminescence and Applications,Changchun Institute of Optics,Fine Mechanics and Physics,Chinese Academy of Sciences,State Key Laboratory of Luminescence and Applications,Changchun Institute of Optics,Fine Mechanics and Physics,Chinese Academy of Sciences,State Key Laboratory of Luminescence and Applications,Changchun Institute of Optics,Fine Mechanics and Physics,Chinese Academy of Sciences,State Key Laboratory of Luminescence and Applications,Changchun Institute of Optics,Fine Mechanics and Physics,Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:对具有InGaAs/GaAsP量子阱周期增益结构有源区的980 nm电泵浦垂直外腔面发射激光器(EP-VECSEL)的振荡特性进行了理论分析及实验研究.模拟并分析了耦合腔条件下EP-VECSEL的振荡特性与其分布布拉格反射镜(DBR)及外腔镜反射率之间的关系，并根据理论分析结果对器件结构进行了优化设计.在实验上制备出具有不同外腔镜反射率的EP-VECSEL器件，并对其连续波(CW)振荡特性进行了研究.实验结果表明，有源区直径为300 μm的EP-VECSEL器件在外腔镜反射率为90 %时阈值电流为1.2 A，注入电流为4 A时连续激光输出功率为270 mW; 在外腔镜反射率为95%时阈值电流为0.9 A，4 A下输出激光功率为150 mW.实验结果与理论分析结论符合较好，说明本文采用的理论分析方法能有效模拟及优化EP-VECSEL器件的振荡特性. Abstract:The oscillation characteristics of 980 nm electrically-pumped vertical-external-cavity surface-emitting laser (EP-VECSEL) with periodic gain structure active region of InGaAs/GaAsP quantum well was analyzed theoretically and experimentally. The relationship between the DBR & external cavity mirror reflectivity and the oscillating characteristic characteristics of the EP-VECSEL with coupled cavity was simulated. Furthermore, based on the results of simulation, the device structure was optimized. EP-VECSEL devices with different external cavity reflectivity were fabricated and the continuous-wave (CW) oscillation output characteristics were studied. The results of experiment indicated that the threshold current of the 300 μm-device with 90% external mirror reflectivity was 1.2 A and its output power was 270 mW while under injected current of 4A; the output power of the 300 μm-device with 95% external mirror reflectivity was 150 mW at 4 A of injected current and the threshold current was 0.9 A. The experimental results were in good agreement with theoretical analysis, indicating that the model using in this article is suitable for the optimization of EP-VECSEL’s oscillation characteristics.The oscillation characteristics of 980 nm electrically-pumped vertical-external-cavity surface-emitting laser (EP-VECSEL) with periodic gain structure active region of InGaAs/GaAsP quantum well was analyzed theoretically and experimentally. The relationship between the DBR & external cavity mirror reflectivity and the oscillating characteristic characteristics of the EP-VECSEL with coupled cavity was simulated. Furthermore, based on the results of simulation, the device structure was optimized. EP-VECSEL devices with different external cavity reflectivity were fabricated and the continuous-wave (CW) oscillation output characteristics were studied. The results of experiment indicated that the threshold current of the 300 μm-device with 90% external mirror reflectivity was 1.2 A and its output power was 270 mW while under injected current of 4A; the output power of the 300 μm-device with 95% external mirror reflectivity was 150 mW at 4 A of injected current and the threshold current was 0.9 A. The experimental results were in good agreement with theoretical analysis, indicating that the model using in this article is suitable for the optimization of EP-VECSEL's oscillation characteristics. 参考文献 相似文献 引证文献

Si homojunction structured near-infrared laser based on a phonon-assisted process

We fabricated several near-infrared Si laser devices (wavelength ∼1300 nm) showing continuous-wave oscillation at room temperature by using a phonon-assisted process induced by dressed photons. Their optical resonators were formed of ridge waveguides with a width of 10 μm and a thickness of 2 μm, with two cleaved facets, and the resonator lengths were 250–1000 μm. The oscillation threshold currents of these Si lasers were 50–60 mA. From near-field and far-field images of the optical radiation pattern, we observed the high directivity which is characteristic of a laser beam. Typical values of the threshold current density for laser oscillation, the ratio of powers in the TE polarization and TM polarization during oscillation, the optical output power at a current of 60 mA, and the external differential quantum efficiency were 1.1–2.0 kA/cm2, 8:1, 50 μW, and 1 %, respectively.

中红外连续波光学参变振荡技术研究进展

中红外连续波光学参变振荡技术研究进展

Injection-Current-Induced Blue-Shift Laser Diode: Concept of Excess Carrier Conservation

We report the blue-shift characteristics of continuous-wave oscillation wavelength induced by the current injection of a GaAs-base laser diode. Typical laser diodes show red-shift characteristics owing to the band-gap narrowing induced by a rise in the temperature of the active layer upon current injection. The cause of the blue shift in the laser diode reported here is the effect of the conserved excess-carrier-induced refractive-index reduction, which is superior to the temperature-rising effect. We try to construct a new simple model to explain such blue-shift characteristics.

Control of solid-state lasers using an intra-cavity MEMS micromirror

High reflectivity, electrothermal and electrostatic MEMS (Micro-Electro-Mechanical Systems) micromirrors were used as a control element within a Nd-doped laser cavity. Stable continuous-wave oscillation of a 3-mirror Nd:YLF laser at a maximum output power of 200 mW was limited by thermally-induced surface deformation of the micromirror. An electrostatic micromirror was used to induce Q-switching, resulting in pulse durations of 220 ns - 2 μs over a repetition frequency range of 6 kHz - 40 kHz.

Suppression of continuous lasing in a carbon nanotube polyimide film mode-locked erbium-doped fiber laser

We demonstrated an erbium-doped mode-locked fiber laser using a single-walled carbon nanotube-dispersed polyimide (SWNT-PI) film. Different mode-locking operations were compared and analyzed utilizing SWNT-PI films with different concentrations (2, 1, and 0.25 wt.%, respectively). It was found that the continuous single-pulse mode-locking operation was often accompanied by a continuous wave oscillation part for the 1 and 0.25 wt.% SWNT-PI films, whereas the 2 wt.% SWNT-PI film presented the most excellent mode-locking performance, thanks to sufficient modulation depth. Using the 2 wt.% SWNT-PI film, a stable pulse train with a pulse width of 840 fs and a repetition rate of 15.3 MHz was achieved. The average output power was 0.33 mW at the pump power of 155 mW under an output coupling ratio of 10%. Operational performance of the laser cavity when employing the 2 wt.% SWNT-PI film was also demonstrated.

Photonic bandgap fibre oscillators and amplifiers

In the search for ever higher output power or energy from fibre oscillators or amplifiers a nowadays mature technology relies on enlarging the fibre mode area. Broadening of the core diameter, all other things being equal, inevitably yields a multimode fibre, thereby dramatically limiting the device usefulness. Various strategies have been deployed to design and manufacture single transverse mode fibre oscillators and amplifiers, among which making use of the so-called photonic bandgap effect to restrict the modal population seems promising. Helped by efficient and reliable numerical tools the design of large mode area singlemode photonic bandgap fibres is presented. Two fibres with 20-μm and 40-μm core diameter, both of them heavily doped with Yb 3+ ions, have been fabricated by the widespread modified chemical vapour deposition process and are shown to behave properly when used as the core element of either continuous wave oscillators or femtosecond amplifiers. Good output beam quality (M 2 parameter spanning from 1.12 to 1.5 for the set of fibres studied) and high slope efficiency of 80% in cw oscillation regime are demonstrated. Furthermore the 40-μm core diameter fibre is shown to be resilient to tight bending down to 7.5-cm radius. The stack-and-draw process makes it easy to tailor the outer cladding so that a large numerical aperture can be reached. Subsequently, from this air-clad fibre, 500 fs 47 W pulses at 35 MHz are obtained from a two-stage chirped pulse amplification system.