External cavity coupling and phase locking of gallium arsenide injection lasers

The techniques involved in phase locking large multi-element junction laser arrays will be described. Specific mention is given to external cavity coupling, laser uniformity, physical dimensions, and array configuration. As a result, it has been found that a far more ideal beam pattern can be obtained from large diffraction-limited diodes than from a linear array of small ones. A coupled five-element array of 25-mil-wide units operated at-30°C has emitted 19 watts of peak power in a set of common modes.     

光纤激光器光场谐振中的附加相移

一、引言 光纤激光器作为一种新型激光器或有源光纤器件为国内外研究者所注目。自80年代以来,从光纤激光器的激活介质到工作形式都有较大的发展。但所研究的激光器一般分为两类:掺杂晶体光纤激光器和掺杂玻璃光纤激光器。谐振腔的形式既有在光纤端面镀反射膜的封闭腔式,也有将光纤置于通常谐振腔的外腔式。光纤激光器与普通激光器的不同点在于:光场在腔内不仅受到反射镜的限制,还受到光纤波导的约束。本文从光纤激光器光场谐振条件出发,提出了光纤激光器中存在光场谐振中的附加相移,并导出了谐振频率与光纤波导参数的关系。     

利用模糊算法实现光学谐振腔锁定优化（特邀）

光学谐振腔不仅可以增强激光和物质的相互作用,而且能够抑制激光的噪声,是开展精密测量、量子光学等研究的重要工具。激光和光学谐振腔共振的稳定锁定是其应用的关键。然而,在实际环境中锁定效果会受机械振动、温度变化等因素的影响。提出了将模糊算法应用于PDH （Pound-Drever-Hall）技术,使比例积分微分控制器的三个参数能够根据外界环境变化进行调节以实时获得最优参数,有效提升了光学谐振腔的锁定的抗干扰能力。如果外界干扰仍然过大以至于失锁,系统可以使其自动重新锁定。该系统有效增强了光学谐振腔的实用性,为光学谐振腔在精密测量、量子光学实验中的应用提供了技术基础。     

LD端泵固体激光器谐振腔的选择

运用传播圆-变换圆的理论对LD端泵固体激光器常用的三种谐振腔（平平谐振腔、左凹右平谐振腔、左平右凹谐振腔）和左凸右平谐振腔的腔型结构及相关结构参数对激光器输出功率与模式特性的影响做出了系统的分析。得出腔长较短的谐振腔激光输出功率较大而且可有稳定的TM00输出,以及左凹右平谐振腔和左凸右平谐振腔具有光学镇定器的作用。用平平谐振腔固体激光器所做的实验结果与用传播圆-变换圆的分析结论相符。对今后如何获取激光器优化输出特性有一定的意义。     

Monolithic integration of microlensed resonant photodetectors andvertical cavity lasers

Monolithic integration of high performance microlensed resonant photodetectors and vertical cavity lasers (VCLs) from a single epitaxial growth is presented. The VCLs have sub-200 μA threshold currents. Adjacent detectors have the same operating wavelength and responsivities of ~0.4 A/W with ~6 nm optical bandwidths     

耦合强度对公共环形腔耦合式光纤激光器锁相性能的影响

利用公共环形腔耦合实现了两路光纤激光器的无源相位锁定,研究了激光器之间耦合强度对锁相性能的影响。环形耦合腔主要由两个22的光纤耦合器组成,其构成了激光器之间能量相互注入耦合的公共通道,并使它们获得了初步的相位同步。考虑到耦合强度主要由成环光纤耦合器的耦合比决定,建立了分析耦合强度影响的理论模型,并从理论上研究了耦合比的大小和差异对环内光强和输出光强的影响。此外,实验上实现了两路掺铒光纤激光器的有效相位锁定,并通过分析远场干涉光斑和输出功率研究了锁相阵列输出激光束的相干性和合成效率。研究结果表明:足够的能量耦合强度是获得有效相位锁定的必要条件,通过增加耦合比来增大耦合强度可以提高锁相阵列的相干性,但会略微降低合成效率。     

Mode description of routes to chaos in external-cavity coupledsemiconductor lasers

The nonlinear behaviors of routes to chaos in semiconductor lasers with external optical feedback were explored in this work. It was indicated that the relaxation oscillation was the origin of the first nonlinear instability of optical intensity under a short delay. Three types of transition routes with quasi-periodic, subharmonic oscillation, and periodic doubling to optical chaos were distinguished in terms of the delay time normalized to the inverse of the relaxation oscillation frequency of a solitary laser diode. The linearized mode theory and small-signal response were confirmed as part of the phenomena in the transitions to chaos     

Passive phase locking of an array of four fiber lasers by mutual injection locking

In this paper, we report the passive phase locking of a four fiber lasers array by mutual injection locking. The four fiber lasers are mutually injected by four 5/5/90 couplers. Through mutual injection locking, good coherence has been obtained in the far field. The four fiber lasers can operate at the same wavelength with a stable output power. This scheme is quite easy to implement and can be extended to combine more beams.     

Coupled oscillators at a distance: applications to coupledsemiconductor lasers

A theory for coupled oscillators is developed and applied to data for coupled semiconductor lasers. The theory generalizes much of the early work on this subject, as it includes the effects of time delays along the coupling path. By allowing for these time delays, additional degrees of freedom, or longitudinal modes are introduced in the coupled oscillator system. It is shown that quality phase locking requires that only one coupled-cavity mode be excited in the system, and that this limits the allowable levels of coupling to a range that extends from the minimum at which locking first occurs (the Adler condition) to a maximum coupling at which the lock begins to degrade; this latter level occurs only in oscillators coupled at a distance     

Passive mode locking of lasers with the optical Kerr effect modulator

A detailed analytical investigation is presented of a nonlinear device termed the optical Kerr effect modulator (OKEM) which is used to passivelyQswitch and mode lock high-power lasers. Experimentally, an OKEM employing two standard quarter-wave plates is used to passively mode lock the Nd:glass laser. The mode-locking threshold dependence upon the parameters of the OKEM transmission function is definitively established. Pulsewidths and spectral measurements are given for the train of ultrashort pulses from the glass laser mode locked with the OKEM using two different Kerr liquids. The analytical and experimental results together indicate that the OKEM technique is a versatile and viable alternative and in addition overcomes most of the shortcomings intrinsic to the saturable absorber technique. The non-resonant nature of the OKEM suggests that it should find immediate application as a passiveQ-switching and mode-locking element for a Variety of lasers, including dye lasers, UV lasers, the CO2laser, and, notably, the high-power iodine laser.     

Effects of resonant mode coupling on optical Characteristics of InGaN-GaN-AlGaN lasers

The phenomenon of resonant mode coupling is modeled and numerically investigated in InGaN-based multiple-quantum-well laser structures. It is shown that under resonant conditions, the internal mode coupling can lead to severe distortions of both near- and far-field characteristics. Taking into account the carrier-induced change of the modal effective index for the lasing mode, we show that the resonant internal mode coupling can result in a strongly nonlinear dependence of the modal gain on injection current, with possible region of negative differential modal gain.     

Direct optical frequency modulation and injection locking of resonant tunnel diode oscillator

Preliminary results indicate that a resonant tunnel diode (RTD) oscillator can be optically tuned, frequency modulated, and injection locked. Experiments were performed in which a 2.8 GHz RTD oscillator was frequency modulated from DC to 100 MHz and injection locked over a 150 kHz bandwidth with a laser diode via fibre optics.<>     

Multiple-input optical control of vertical cavity surface emitting lasers using intracavity-coupled in-plane lasers

We report new experimental results demonstrating optical bistability and two-input NOR gate operation in intracavity-coupled in-plane and vertical cavity surface emitting lasers (VCSELs) fabricated from the same epitaxial material. The VCSEL (or output) section gain is controlled by separately biased in-plane laser section(s), and depending on the in-plane power output, complete quenching of stimulated emission in the VCSEL is observed. Hysteresis is present in the VCSEL output power versus in-plane laser input power characteristic, and an optical memory effect is observed in the combined device.     

Nonlinear injection locking dynamics and the onset of coherencecollapse in external cavity lasers

A theoretical analysis is presented of the experimentally observed collapse of coherence in semiconductor lasers exposed to moderate optical feedback. A main point in the analysis is, that coherence collapse in the delayed-feedback (DFB) system shows up as bistability in a much simpler model which corresponds to an injection locking system. Based on this, the authors derive a simple analytical expression, valid for DFB as well as Fabry-Perot lasers, for the critical feedback level at which coherence collapse sets in. Simulations of the nonlinear injection locking model reveal the presence of complicated nonlinear dynamics with period-doubling bifurcations and coexisting attractors even inside what is normally denoted the stable locking range     

沟道台面衬底三段大光腔激光器

本文报道了一种新型结构的半导体激光器——沟道台面衬底三段大光腔激光器,它具有阈值电流低、高输出功率和易获得基横模单纵模工作的特点.     

GaN resonant cavity light-emitting diodes for plastic optical fiber applications

The optical designs of resonant GaN light-emitting diodes (LEDs) have been determined for maximum extraction efficiency into typical plastic optical fiber of numerical aperture 0.5. An optimum extraction efficiency of 3.9% can be achieved for a practical resonant cavity LED (RCLED), taking account of current growth and processing considerations. The optimized device is a metal-active layer distributed Bragg reflector construction. Constructive interference effects from the top metal mirror are found to play the dominant role in efficiency enhancement. The extraction efficiency of an optimized resonant single-mirror LED is found to be 3.3%, indicating a small compromise in performance compared with the more complex RCLED structure.     

相位锁定至超窄线宽激光的高相干性双光梳研究

研究并实现了一种相位锁定至超窄线宽激光的双光梳系统。实验通过将两台重复频率约为200MHz、重复频率差约为17 kHz的掺铒锁模激光器的对应梳齿,同时分别锁定到两台不同波长(1542 nm和1560 nm)的窄线宽连续激光器上,实现了相位相干且稳定度高的双光梳。锁定后单台光梳的梳齿线宽均低于5Hz(受限测试条件),两台光梳的相对线宽小于0.35Hz。该双光梳系统对于高精度光谱分析、时频传递,尤其是绝对距离测量等领域具有重要的应用价值。     

Reduction of optical phase noise in semiconductor lasers

There are several applications of highly coherent semiconductor lasers, especially in coherent optical-fibre communications systems and optical-fibre sensors. Optical phase noise is extremely important in these applications. Here we report preliminary results from a simple technique whereby phase noise in semiconductor lasers may be reduced. Initial results demonstrate a phase-noise reduction of typically 20 dB. Developments of the technique should permit reduction towards the shot noise limit.     

Injection locking characteristics of semiconductor lasers in double phase conjugate mirror geometry

Phase locking of two semiconductor lasers is demonstrated by injection of the feedback from a double phase conjugate mirror. The stability or quality of the locking is characterised from fringe visibility measurements. Phase conjugate injection into the central mode exhibits an asymmetric stable locking region which extends to greater detunings and asymmetry with increased feedback. High quality locking is also demonstrated by phase conjugate injection into sidemodes up to nine longitudinal mode spacings from the target mode.<>