High-density wavelength switching obtained from a tunable multisection laser diode

We describe a method based on multistability in wavelength for obtaining high-density wavelength switching for application to signal routing. The method relies on the use of a 1550-nm wavelength-tunable multielectrode laser diode that is fed back electrically. The system operates as a multistable device that exhibits multiple steady states in wavelength. The device can be used to convert time-multiplexed packets into wavelength-multiplexed signals.     

A power and wavelength detuning-dependent hysteresis loop in a single mode Fabry-Prot laser diode

In this paper, we observe experimentally the optical bistability induced by the side-mode injection power and wave-length detuning in a single mode Fabry-Prot laser diode (SMFP-LD). Results show that the bistability characteristics of the dominant and injected modes are strongly dependent on the injected input optical power and wavelength detuning in an SMFP-LD. We observe three types of hysteresis loops: counterclockwise, clockwise, and butterfly hysteresis with various loop widths. In the case of a bistability loop caused by injection power, the transition from counterclockwise to clockwise in the hysteresis direction with the wavelength detuning from 0.028 nm to 0.112 nm is observed in a way of butterfly hysteresis for the dominant mode by increasing the wavelength detuning. The width of hysteresis loop, induced by wavelength detuning is also changed while the injection power is enhanced from 7 dBm to 5 dBm.     

Tunable diode laser spectroscopy with optimum wavelength scanning

In this paper, an improved signal processing method is given, aiming at a sensitivity improvement of the tunable diode laser spectroscopy based gas concentration measurement. The gas absorption spectrum is probed with an optimum wavelength scanning function which enables a more efficient curve fit than for traditional linear wavelength scanning. The wavelength scanning function is determined to be optimum, in the sense that the variance of the estimated concentration noise is minimized. This optimum scanning function depends on the signal model used in curve fitting. Several models including interfering gas spectra and etalon fringes are examined. Compared to the gas absorption spectrum recorded by ramping the wavelength linearly, the optimum spectrum waveforms have a cascade structure, which means that the optimum scanning preferably samples important points of the spectrum. The new method theoretically enables a factor of ～2 improvement on detection sensitivity of the estimated concentration. Furthermore, direct spectroscopy is superior to second harmonic detection, because the concentration noise can be an additional factor of ～2 lower.     

Brewster fringes from a single plate

An autocollimation system with an illuminated circular entrance aperture located in the front focal plane of a lens L is considered. In the middle between S ₀′ and L, a transparent plate a few millimeters thick is placed at an angle of i ₀ = 45° to the axis of the system, and, near the rear focal plane of the lens L, a plane reflecting mirror is placed. The plate divides the primary beam into parts during its propagation both forward and backward (after the reflection from the mirror). This ensures the formation of derivative beams that propagate toward an ocular and that are overlapped in the region of spatially separated images S ₀, S ₁, and S ₂. The possibility of formation of a high-contrast system of first-order two-beam interference fringes in the region of S ₂ is discussed. Conditions for achieving this result are also discussed.     

Integrated wavelength monitoring in a photonic-crystal tunable laser diode

A photonic-crystal tunable 1.55 μm laser diode is fitted with a wavelength monitor on its rear side. The 250-μm long laser based on a coupled-cavity design has approximately 15 nm tunability. The wavelength monitor collects and differentially feeds two-photodetecting areas, thanks to a mode conversion to a higher-order mode (a mini-stopband), followed by tunneling through a thin clad. The layout is numerically optimized to minimize unwanted reflections. Electrical cross-talk was prevented through guard rings and trenches. The correlation between wavelength and the monitor photocurrent ratio demonstrates a 10–20 GHz stabilization capability, or a 15 nm monitoring range.     

Near-diffraction-limited diode laser arrays by wavelength beam combining

We demonstrate 35 W output peak power with M2 approximately 1.35 in both dimensions from a 100 element, 100 microm pitch slab-coupled optical waveguide laser diode array using wavelength beam combining.     

半导体激光器波长稳定系统的反馈效率

反射式体布拉格光栅(VBG)是改善半导体激光器(DL)输出光谱特性的首选器件。对快轴准直透镜(FAC)的非球面方程进行了数值拟合,采用光线追迹的方法建立了DL波长稳定系统反馈效率的计算模型,分析了FAC透镜、反射式VBG的空间位置和旋转角度变化对DL波长稳定系统反馈效率的影响,给出了波长稳定系统中FAC和反射式VBG的装调容差范围。分析结果表明:反射式VBG的空间位置偏差对反馈效率影响不大,但FAC透镜的空间位置和旋转角度偏差、反射式VBG的旋转角度偏差会造成反馈效率的急剧下降。     

半导体激光器波长稳定系统的反馈效率

反射式体布拉格光栅(VBG)是改善半导体激光器(DL)输出光谱特性的首选器件。对快轴准直透镜(FAC)的非球面方程进行了数值拟合,采用光线追迹的方法建立了DL波长稳定系统反馈效率的计算模型,分析了FAC透镜、反射式VBG的空间位置和旋转角度变化对DL波长稳定系统反馈效率的影响,给出了波长稳定系统中FAC和反射式VBG的装调容差范围。分析结果表明：反射式VBG的空间位置偏差对反馈效率影响不大,但FAC透镜的空间位置和旋转角度偏差、反射式VBG的旋转角度偏差会造成反馈效率的急剧下降。     

Approach to optical interference fringes reduction in diode laser absorption spectroscopy

The advantage of a new scheme for balanced detection has been investigated to reduce the influence of optical interference fringes when performing diode laser gas absorption spectroscopy employing lock-in amplifiers and pigtailed lasers. The influence of the fringes has been reduced by comparing the lock-in 2 f signal due to the gas sample with that of a reference beam. The frequency regions outside the absorption feature have been used to obtain information on the interference fringe impact on the signal of interest. We have demonstrated an efficient way to reduce the influence of such fringes by employing this technique combined with non-linear signal processing methods. The different steps of the algorithm are presented. In the experimental arrangement presented, a reduction of the optical interference fringes by about 10 times is achieved, as demonstrated in measurements on molecular oxygen around 761 nm. The new technique is compared with an analog technique for balanced detection and certain advantages of the computer algorithm are pointed out. In particular, the emerging field of gas spectroscopy in scattering solid media strongly benefits from the technique presented. PACS 42.55.Px; 39.30.+w; 42.25.Hz     

808 nm高占空比大功率半导体激光器阵列

采用渐变折射率分别限制单量子阱宽波导结构,通过降低非辐射复合、有源层载流子泄露、散射和吸收损耗来提高出射效率和降低激光阈值电流,从而提高半导体激光器阵列的输出功率;同时使P面具有更高的粒子掺杂数密度,优化N面合金条件,降低半导体激光器的串联电阻,降低焦耳热,提高了半导体激光器阵列的转换效率。利用金属有机化学气相淀积技术生长GaInAsP/InGaP/AlGaAs渐变折射率分别限制单量子阱宽波导结构激光器材料,利用该材料制成半导体激光线阵列在20%高占空比的输入电流下,半导体激光器的输出峰值功率达到189.64 W(180 A),斜率效率为1.1 W/A,中心波长为805.0 nm,阈值电流为7.6 A,电光转换效率最高可达55.4%;在1%占空比的输入电流下,阵列的输出峰值功率可达324.9 W(300 A),斜率效率为1.11 W/A,阈值电流为7.8 A,电光转化效率最高达55.6%,中心波长为804.5 nm。     

Rapid infrared wavelength access with a picosecond PPLN OPO synchronously pumped by a mode-locked diode laser

We theoretically and experimentally investigate wavelength tuning of synchronously pumped optical parametric oscillators (OPOs) on changing the cavity length or the pump-repetition rate. Conditions for rapid and wide-range wavelength access are derived. Using an OPO pumped directly by a mode-locked diode-laser master-oscillator power-amplifier (MOPA) system, an all-electronically controlled access to near- and mid-infrared wavelengths is demonstrated. The singly (signal) resonant OPO is based on periodically poled lithium niobate (PPLN) and emits 8 ps idler pulses at a repetition rate of 2.5 GHz in the wavelength range 1986 to 2348 nm (signal: 1530 to 1737 nm). Wavelength tuning over 114 nm (signal) and 189 nm (idler) is achieved solely by electronically varying the repetition rate of the diode-laser oscillator over 720 kHz. By controlling the repetition rate with a programmable driver, an arbitrary emission sequence of the OPO on two wavelength channels is generated, with access times as short as 10 μs. 11 OPO wavelengths equally spaced in the range 1627–1689 nm (signal) or 2054–2154 nm (idler) could be addressed. Received: 6 September 2000 / Revised version: 16 March 2001 / Published online: 23 May 2001     

Doppler cooling a single Ca+ ion with a violet extended-cavity diode laser

We present a scheme for employing a violet extended-cavity diode laser in experiments with single, trapped ions. For this the grating-stabilised laser is spatially and spectrally filtered and referenced to a Fabry–Pérot cavity. We measure an upper limit to the line width by observing a 305-kHz FWHM beat note with the second harmonic of a titanium sapphire laser. The laser is subsequently used to optically cool a single ⁴⁰Ca⁺ ion close to the Doppler limit. PACS 03.67.Lx; 32.80.Pj; 42.55.Px     

Photorefractive power transfer from parallel laser diode amplifiers into a single output beam

Photorefractive BaTiO(3):Ce was used to combine coherently a signal beam and two amplified pump beams at lambda=678 nm. The master laser beam was split and then amplified in two semiconductor laser amplifiers with gain of as much as 6. The amplifiers were made from quantum-well laser chips by use of antireflection coating. 40% of the power could be transferred to the signal beam without transferring the phase distortions of the pump beams.     

Tunable dual wavelength emission and bandwidth narrowing of a laser diode array with a simple external cavity

We report on the performance of a commercial, non-AR-coated diode laser bar of 20 W output power, consisting of 20 emitters, which uses an external cavity to achieve tunable, dual-wavelength emission. The separation between the wavelength peaks can be continuously tuned from 0 nm to 5 nm. An output power of 2.9 W is achieved at 3.7 nm peak-to-peak separation and higher powers are achieved for less separation. This is the highest dual wavelength output power reported so far using a standard diode laser array. PACS 42.55.Px; 42.60.-v; 42.60.Da; 42.60.Fc     

Rapid wavelength scanning based on acousto-optically tuned external-cavity laser diode

High-speed, wide-range wavelength scanning is demonstrated using a laser diode with an antireflection coating and an external cavity employing an acousto-optic deflector. The narrow spectral width of 0.2 nm observed in the experiment indicates the availability of a highly coherent laser beam. The scanning range of 15 nm under rapid modulation is confirmed in the prototype system. A tuning rate of more than 100 kHz is achieved without any mode hops. To the best of our knowledge, no such high-speed wavelength tuning based on an acousto-optical configuration has been demonstrated thus far.     

Comprehensive electro-optical analysis of long wavelength GaInNAs edge-emitting laser diode

Comprehensive analysis of GaInNAs edge-emitting laser operating near 1300 nm wavelength are made to underline the behavioural features of the proposed laser device, in view of the analytical investigation for various material and device electrical-optical parameters analysis such as band diagram, material gain, quantum well emission wavelength, optical wave and mode profiles, light-current-voltage characteristic, output mode spectrum, current distribution and far-field profile. The material analysis indicates that a high quality GaInNAs active region is designed, where high material gain and photoluminescence wavelength near 1.3 μm are achieved. The device obtains low threshold current operation with lasing emission around 1.285 μm.     

940nm波长高功率线阵二极管激光器封装研究

对940nm波长高功率线阵二极管激光器的封装结构进行了重新设计,并在此基础上开展了芯片的封装实验。封装出的线阵二极管激光器,在连续工作时输出激光功率达40W,在准连续工作时（占空比0.5%）,输出峰值功率可达100W。     

940nm波长高功率线阵二极管激光器封装研究

 对940nm波长高功率线阵二极管激光器的封装结构进行了重新设计，并在此基础上开展了芯片的封装实验。封装出的线阵二极管激光器，在连续工作时输出激光功率达40W，在准连续工作时（占空比0.5%），输出峰值功率可达100W。     

60-W continuous wave laser diode arrays emitting at a wavelength of 808 nm

Samples of cw laser diode arrays (LDAs) with an output power higher than 60 W emitting in the spectral range of 808 nm are developed and fabricated. Main output parameters, including light–current, current–voltage characteristics, and emission spectra of a lot of 5 LDAs are measured.     

260W波长锁定光纤耦合输出泵浦模块实验研究

半导体光纤耦合输出泵浦源是光纤激光器的核心器件,其性能直接制约光纤激光器的输出水平。采用COS封装的高功率LD芯片,通过VBG外腔光谱锁定和精密光束整形变换技术,结合偏振合束与精密聚焦耦合技术将18个LD单元耦合进105 μm/NA0.22光纤,获得不低于260 W功率输出。实验表明,该模块在注入电流18 A时,可获得稳定输出连续功率264 W,对应电光效率52%,输出光谱中心波长975.92 nm,谱宽0.51 nm。该设计为获得高功率、高亮度波长稳定泵浦源提供了一条可行途径,光纤耦合输出模块工程化后可广泛应用在光纤激光器泵浦等领域。