Extended Tunability in a Two-Chip VECSEL

We demonstrate a widely tunable vertical-external-cavity surface-emitting laser (VECSEL) with a W-shaped cavity, in which two VECSEL chips serve as fold mirrors and a birefringent filter is inserted at Brewster's angle. These two chips provide much higher modal gain and broader bandwidth of the gain than a single chip does, enhancing the VECSEL tuning range and reducing the variation of tunable output power with the tuned wavelength. This two-chip VECSEL configuration makes it possible to shape the modal gain spectra of the laser or to manipulate the tuning curve of the laser by two different chips with certain gain peak detuning (offset). Multiwatts high-brightness linearly polarized output with a tuning range of 33 nm is demonstrated in such a two-chip VECSEL     

Continuously tunable photopumped 1.3-μm fiber Fabry-Perotsurface-emitting lasers

Continuously tunable, single-frequency, optically pumped semiconductor-fiber lasers are demonstrated that embody a half-cavity, vertical-cavity surface-emitting laser within a fiber Fabry-Perot cavity. Continuous wavelength tuning over 40 nm at 1300-nm wavelength region is obtained under continuous-wave operation     

垂直外腔面发射半导体激光器的热管理方法研究

垂直外腔面发射半导体激光器在高功率运转的同时可以保持良好的光束质量,近年来一直成为研究的热点。本文介绍了垂直外腔面发射半导体激光器的结构及运行原理。由于热管理是其高功率运行的主要限制因素之一,分析了垂直外腔面发射半导体激光器的热管理方法。使用反向生长的外延片通过化学湿法腐蚀去掉砷化镓衬底,得到了约6μm左右的外延片,最后利用808nm的泵浦光进行抽运获得了200mW的连续激光输出。     

Characterization of wavelength-tunable single-frequency fiber laser employing acoustooptic tunable filter

This paper demonstrates and characterizes a novel wavelength-tunable single-frequency erbium-doped fiber ring laser incorporating an all-fiber acoustooptic tunable bandpass filter and a self-constructed saturable absorption grating (SAG). Stable single-longitudinal-mode operation was achieved over the wavelength range of 48 nm with a sidemode suppression ratio higher than 50 dB. The wavelength tuning characteristics, and the laser dynamics in wavelength switching and sweeping are analyzed in detail. A theoretical analysis on the effect of the SAG is also described.     

Tunable single- and double-frequency diode-pumped Nd:YAG lasers

An Nd:YAG 1-cm-long crystal has been used as the active medium for tunable single- and double-frequency lasers with a metallic absorbing thin-film selector. Cobalt and chromium thin films (210-nm thickness) were used for mode number and frequency control. The laser with a short cavity (25 mm) provided slow smooth tuning up to 6 GHz, the frequency chirp up to 4 GHz with repetition rate about 0.5 kHz and hop tuning over 150 GHz at a maximum pump power of 1.8 W. 520 mW of single-frequency output power was achieved. Double-frequency operation with a space of 1.5-2.5 GHz was realized in a laser with cavity length up to 100 mm     

Widely tunable single-frequency Er-doped fiber laser with longlinear cavity

A widely tunable single-frequency Er-doped fiber laser is demonstrated in a 21-m-long linear cavity incorporating all-fiber acoustooptic frequency shifters and a saturable absorption grating. Stable single-frequency operation is achieved with a sidemode suppression ratio higher than 50 dB and a wavelength tuning range greater than 40 nm     

Tunable erbium-doped fiber ring laser precisely locked to the 50-GHz ITU frequency grid

A discretely tunable, single-frequency erbium-doped fiber ring laser demonstrates frequency locking to the 50-GHz ITU frequency grid with an accuracy of /spl plusmn/0.3 GHz and stability of /spl plusmn/0.05 GHz over a 50-nm tuning range. An output power of 7 mW and an extinction ratio of 45 dB make this single-frequency laser useful for a variety of DWDM applications.     

230-mW diode-pumped single-frequency Er:Yb laser at 1.5 μm

We report on a diode-pumped Er:Yb laser able to generate a single-frequency output power in excess of 200 mW at both 1.53 μm and 1.56 μm and over 300 mW in multimode operation. The tuning characteristics of the source are reported and discussed. The relative intensity noise presents in all configurations a peak value lower than -92 dB/Hz and its level decreases below -160 dB/Hz for frequencies higher than 8 MHz     

20 dBm linearly polarised tunable single-frequency diode-pumpedEr:Yb laser at 1535 nm using anisotropic absorptive intracavity etalon

A linearly polarised single-frequency diode-pumped Er:Yb bulk laser with output power in excess of 100 mW has been demonstrated. The use of an anisotropic absorptive intracavity etalon to achieve both single-frequency operation and linearly polarised output is investigated. Output power and tuning characteristics as well as relative-intensity noise measurements are reported. A new active medium, based on a new glass host with reduced pump-induced birefringence, allowed for negligible performance degradation when using the anisotropic etalon instead of a standard BK7 etalon. A broad tuning range and a relative-intensity-noise peak of about -90 dB/Hz has been achieved     

Experimental Investigation and Analytical Modeling of Excess Intensity Noise in Semiconductor Class-A Lasers

Excess intensity noise in a low-noise single-frequency class-A VECSEL is experimentally investigated over the frequency range 10 kHz-18 GHz. An analytical model is derived, based on multimode Langevin equations, to describe the observed laser excess noise over the whole bandwidth. From 50 MHz to 18 GHz, class-A operation leads to a shot noise limited relative intensity noise (RIN), namely -155 dB/Hz for 1-mA detected photocurrent, except at harmonics of the cavity free spectral range (FSR). At these frequencies, the excess noise is shown to be due to the amplified spontaneous emission contained in the nonlasing side modes. The measured levels of excess noise correspond to side mode suppression ratios (SMSRs) ranging from 70 to 90 dB, in agreement with the model. At low frequencies, 10 kHz-50 MHz, the observed excess noise spectrum has the expected Lorentzian shape. Its bandwidth increases with the pumping rate to an upper limit given by the cavity photon lifetime. Below this cutoff frequency, we show that the pump RIN is the dominant source of noise, while it is filtered by the laser dynamics above. Finally, our model permits to design a semiconductor class-A laser with an intensity noise limited to the shot noise level over the whole 10 kHz-18 GHz bandwidth.     

Tunable single-frequency Yb:YAG laser with 1-W output power usingtwisted-mode technique

A diode-pumped, single-frequency Yb:YAG laser with >1-W CW output power has been demonstrated. Single-frequency operation is induced by using the twisted-mode technique, and an etalon has also been inserted into the cavity for timing. Single-frequency tuning from 1.02898-1.03174 μm has been achieved with a 116-μm-thick etalon; the tuning range was limited by the etalon's free spectral range     

Single frequency electrooptical tuning of an extended cavity diodelaser at 1500 nm wavelength

A wavelength-tunable, single-frequency GaInAsP-InP laser diode using an intracavity electrooptic LiNbO₃ crystal as the wavelength selective component is discussed. Wavelength tuning is achieved by applying a driving voltage on the crystal electrodes. First results indicate a tuning rate of 1 GHz/V over a tuning range of about 4 nm. This performance was obtained using a nonoptimized X-cut, Z-propagating LiNbO₃ crystal. A potential tuning rate of 6.5 GHz/V is possible with reasonable improvements     

1.5 ?m wavelength GaInAsP C3 lasers: single-frequency operation and wideband frequency tuning

We have characterised the temporal-spectral behavior of 1.5 ?m wavelength cleaved-coupled-cavity (C3) lasers. Single longitudinal mode discrimination ratios in excess of 500:1 have been obtained under high bit rate modulation. Bit error rate of less than ? 10?9 were obtained under single-frequency operation with direct modulation up to 1 Gbit/s. Averaged frequency tuning rates as large as 26 ?/mA and frequency tuning excursion of 300 ? were achieved when the C3 laser was operated in a frequency modulation mode.     

Performance characteristics of a 1.5 μm single-frequencysemiconductor laser with an external waveguide Braff reflector

Single-frequency operation of 1.5-μm semiconductor lasers was obtained by combining a regular Fabry-Perot laser to an external waveguide Bragg reflector. The laser is characterized by very pure single-frequency operation, 10-MHz linewidth, and greatly-reduced frequency chirp under direct modulation. The laser has been tested in 1.7-Gb/s transmission experiments over 82.5 km of fiber     

Single transverse mode operation of electrically pumped vertical-external-cavity surface-emitting lasers with micromirrors

We report an electrically pumped vertical-external-cavity surface-emitting laser (VECSEL) that is designed for wafer-scale fabrication. Single-mode continuous-wave operation is demonstrated at a wavelength of 970 nm. The device structure incorporates a curved micromirror output coupler that is produced using a micromolding process. In addition to outlining the VECSEL fabrication process, we quantify its spatial and spectral modal characteristics.     

The mechanism of single-frequency operation of the hybrid-CO2laser

The mechanism of a new method of obtaining high-power single-frequency pulses from a TEA-CO2laser is discussed. Measurements of the shape and monochromaticity of pulses from the hybrid laser which has both a TEA and a low-pressure gain section inside one resonator are presented. The mechanism of single-frequency operation of the hybrid laser is discussed with reference to numerical solutions of simplified rate equations. The low-pressure section provides gain only over a narrow range of frequencies so that a mode lying in that bandwidth builds up faster than neighboring modes to give a single-frequency pulse resembling in overall shape the normal TEA laser pulse. If the system is already lasing when the TEA discharge begins, the single-mode radiation already present rapidly grows to give a single-frequency pulse lacking a gain-switched peak.     

Single-frequency, single-knob tuning of a CW color center laser

We describe a simple way to achieve CW single-frequency laser operation with a grating as the sole tuning element. It is Shown, both experimentally and theoretically, that by proper choice of cavity parameters, the competing hole burning modes can be completely suppressed. Experiments to demonstrate the theoretical calculations were carried out in a CW color center laser using Tl⁰(1) centers. Linewidths of 0.01 cm^-1were obtained and this figure can probably be much improved by proper cavity stabilization. The method can be readily extended to any compact gain medium.     

可调谐单频掺镱光纤DBR激光器

对分布布拉格反射(DBR)的透射特性进行了分析,制作了一个单频窄线宽掺镱光纤DBR激光器.在977 nm半导体激光器泵浦下,在1052.5 nm波长处输出功率可达4 mW,线宽小于8 MHz(受测量仪器分辨率限制).采用弧形梁调谐光纤光栅,实现了DBR光纤激光器在单纵模工作状态下的连续调谐,调谐范围可达20.4 nm(1036.1～1056.5 nm),并研究了调谐对激光器的泵浦阈值和斜率效率的影响.     

外腔反馈式单频掺Er3 光纤激光器的优化设计

设计了以光纤Bragg光栅(FBG)作为外腔反馈元件的单频Er^3 光纤激光器，并对其进行了数值模拟。分析表明，采用FBG外腔结构可以实现稳定、无跳模的单频运转，且在一定范围内外腔越长、激光线宽越窄。为了获得较高的单频激光输出功率，将输出的信号光继续通过一段Er^3 光纤，利用剩余泵浦光对其放大。理论模拟得到单频输出功率为0．373mW，比放大前提高了7dB，斜率效率0．75％。     

Novel Gain Medium Design for Short-Wavelength Vertical-External-Cavity Surface-Emitting Laser

We report on a novel material developed as the gain medium for a vertical-external-cavity surface-emitting laser (VECSEL) operating around 850 nm. The new material departs from the conventional approach of using GaAs as the quantum-well (QW) material and expands the previously reported concept of using InAlGaAs QWs. The inclusion of indium pins dislocation propagation into the active region of the VECSEL. Crucial for the success of this design is also the development of indium and phosphorous containing quinternary strain-compensating layers. These surround the QWs and provide a more substantial resistance to defect propagation. Results are presented for stable high-power single spatial mode operation of a laser based on this material together with measurements of the unsaturated gain of the device and the characteristic temperature for the threshold power