无热退偏损耗Nd∶YAG环形腔单纵模激光器

在Nd∶YAG侧面泵浦四镜环形腔单纵模激光器内,采用薄膜偏振片反射光束作为输出光束,以消除环形腔内热退偏损耗,提高输出功率及效率。实验表明,该Nd∶YAG环形腔可单向运转并输出单纵模激光,环形腔激光器内无热退偏损耗。在驱动电流为21 A时,环形腔激光器输出5.1 W 1064 nm单纵模激光,输出激光线宽为200 MHz,输出光束为线偏振光。通过采用端面泵浦结构,以及采用对p偏振光反射率与泵浦功率相匹配的薄膜偏振片,激光器单纵模输出功率及效率可望进一步提高。     

He-Ne多纵模激光器改为单纵模激光器工作时其物理机制的研讨

本文简述几种制做单纵模激光器的方法以及相应的选模原理,并对多纵模激光器改为单纵模激光器后,其输出功率达到原激光器中单个纵模最大输出功率的4倍以上这一现象,从物理机制上作了初步探讨。根据分析比较,认为法珀标准具插入腔内选模将是He-Ne多纵模激光器改为单纵模激光器的较优方案。     

注入连续光实现锁模光纤激光器的波长稳定

提出了一种实现锁模光纤激光器波长稳定的方法,即向锁模激光器腔内注入连续光,使某一组纵模在注入连续光的基础上起振。这组纵模在对增益介质的竞争中可以稳定地占据优势,从而实现激光器输出光谱的稳定。理论分析发现注入连续光会使锁模激光器纵模线宽变大,而线宽的增大将会增加进入纵模的连续光功率。在实验中对基于掺铒光纤放大器(EDFA)的主动锁模光纤激光器进行波长稳定,激光器的调制频率为10.06 GHz,观察到了良好的稳定效果。为进一步检验波长稳定的效果,对锁模光纤激光器进行波长稳定后,将其输出的光信号经过一个法布里-珀罗(F-P)滤波器,稳定地滤出了功率较高的纵模。法布里-珀罗滤波器的自由光谱区(FSR)为40.24 GHz,透射峰3 dB带宽为40 MHz。实验结果证明纵模被稳定在法布里-珀罗滤波器的透射峰范围内,纵模波长的波动小于40 MHz。     

基于CPLD设计实现单横单纵激光器种子注入纵模锁定

基于自滤波非稳腔、种子激光注入及CPLD控制的干涉法纵模锁定技术,研制出一套单横单纵激光器系统；对激光器的工作原理及纵模锁定电路设计进行了说明。该设计具有输出光束质量好,工作稳定,抗干扰性强的特点。该激光器经历了在强干扰环境中长时间的“烤机”实验,单纵模锁定概率达100%。     

激光光谱学的应用:V 超快过程研究

1引言激光的输出一般是由若干个纵模或由纵模、模模组成的多模花样，这些模的振幅、相位都不固定，是激光输出随时间变化而无规则叠加的结果。在多纵模振荡时，如果使振荡模的频率间隔保持一定，并且使模之间保持确定的相位关系，这时激光输出将成为具有一定时间间隔的一列脉冲。这种激光器称作“锁模”或“锁相”激光器[1]。由于锁模激光器产生的脉冲序列，其脉宽松窄，所以人们把它称之为“超短光脉冲”。1965年，Mocher的Collins第一次实现了红宝石激光器的锁模[2]。自那以后，赶快激光技术取得了很大的进展。克尔透镜锁模的Nd：YLF激…     

无拍频1570nm光纤激光器及其在2μm波段激光产生中的应用

实验研究了基于光纤布拉格光栅(FBG)的直接输出1570 nm单波长光纤激光器,采用光纤耦合器搭建塞格纳克宽带反射器并与部分反射光纤光栅构建直腔激光器,通过优化光栅反射率和输出方向实现了最高谐振效率为24.42%、最大输出功率为2.8 W、边模抑制比为65 d B的1570 nm光纤激光直接输出。通过增大腔长增加激光器谐振纵模数量,从而基于纵模间的平均效应实现了1570 nm单波长光纤激光器的稳定无拍频输出,进而利用该激光器作为掺铥光纤的泵浦源实现了2μm波段光纤激光器被动锁模输出。     

半导体激光器的光谱及参数测量

半导体激光器的输出光谱,反映了激光器本身的基本工作特性。本文从实验上研究了半导体激光器的输出光谱特性随偏置电流而变化的关系,并对其进行了理论分析。在此基础上,进一步测得了半导体激光器的热阻,增益峰值波长和纵模波长对载流子密度的相对变化率等基本参量。     

超短腔染料激光器的频率牵引特性

比较了激光增益介质不同增宽类型对激光纵模频率牵引的影响;实验测量了超短腔染料激光器(SCDL)多纵模运转时输出的光谱,分析其频率牵引特性.通过频率牵引特性曲线可测定SCDL的腔长.     

单纵模半导体激光器偏振特性的研究

对双异质结1.3μm单纵模半导体激光器偏振特性的测量表明,在输出光场中电场平行于结平面的Ex模和垂直于结平面的Ey模总是不同程度地同时存在,这对光谱纯度有较大的影响。当加入偏振镜滤除沿y方向偏振的分量后,光谱纯度有所改善,并且这种改善与激光器的工作状态有关。对于这个现象本文给出了定性的分析。     

基于体布拉格光栅选模的单纵模激光器

采用体布拉格光栅(VBG)作为纵模选择元件,组合使用透射式和反射式体布拉格光栅构成窄带滤波器进行纵模的选择,在Nd:YLF激光器中得到了单纵模几率100%,单脉冲能量2 mJ,波长1053 nm的单纵模输出.实验结果表明,体布拉格光栅用作选模元件的同时,又用作输出耦合镜,简化了单纵模激光器的结构,提高了抗干扰能力,且具有大功率输出的潜力.     

New mechanism for bistable operation of closely coupled twin stripe lasers

Evidence for a novel mechanism causing bistable operation of closely coupled twin stripe lasers is reported. Current switched bistable operation has been demonstrated stably at room temperature, through the light beam being switched from a central mode to one where the optical filament crosses diagonally from under one laser stripe to the other.     

Picosecond switching dynamics of a bistable-wavelength-latchtwo-segment distributed feedback laser

The bistable-wavelength-latch operation of a two-segment distributed-feedback laser was observed and characterized. Short electrical trigger pulses were used to demonstrate mode power switching in less than 200 ps with only 450-ps delay between set and reset pulses. Spectrally resolved measurements show transient spectral broadening during the bistable wavelength switching. Fast laser wavelength switching is important for wavelength-division-multiplex photonic switching systems     

Operation of an all-optical bistable device dependent upon incidentand transmitted optical power

The authors describe the optically bistable operation of an all-optical nonlinear Fabry-Perot etalon (NLFP) in which the power-dependent cavity phase shift has a contribution dependent on the power incident on the cavity. When the contributions have the same parity, the optically-bistable behavior is essentially the same as that seen in the now standard bistable NLFP (counterclockwise hysteresis in transmission). For opposite parity there is a range of relative strengths for which bistable operation cannot be obtained, but, outside of that range, bistable behavior having clockwise hysteresis in transmission is possible. This latter bistable behavior is demonstrated, with the NLFP being a GaAlAs laser diode amplifier driven by a similar diode laser. Low-frequency modulation of the laser power by direct variation of the laser drive current produced a small shift in laser wavelength proportional to the laser power, providing the cavity phase shift term proportional to the incident power, while the nonlinear refractive index of the NLFP provided the phase shift proportional to the transmitted power     

Bistable direction switching in an off-axis pumped continuous waveruby laser

A report is presented of the observation of hysteretic bistable direction switching in a single-mode CW ruby laser system. This effect is only observed when the pump beam which is focused into the ruby rod is misaligned with respect to the rod end faces. At low pump powers, the ruby lases in a mode nearly collinear with the pump axis. At a higher pump power the ruby switches to a mode that is collinear with the rod end faces and preserves the original polarization. The effect is large enough to switch the beam by an angle equal to twice the diffraction angle. The observations show that under steady-state pumping, a CW ruby laser can exhibit bistable operation in its output direction and power. A calculation using the heat equation with two concentric cylinders with one as a heat source (pump laser) and the outer wall of the other held at 77K, gives an increase in core temperature of about 0.01 K. Therefore, the increase in temperature is not large enough to change the index of refraction to account for such large macroscopic effects     

Large optical bistability and self pulsations in three section DBRlaser diode

A bistable operation with a hysteresis of 24 mA in the power-current curve of a three section DBR laser is reported. The laser threshold at increasing current is 51 mA while in the opposite direction the laser action is sustained down to 27 mA. The same effect was observed by monitoring the laser threshold through the Bragg and phase section currents. In a large part of the current range which corresponds to the bistable laser operation, strong self pulsations have been observed at frequencies between 1.5 GHz and 3.5 GHz with an amplitude of up to 31.4 dB     

Complementary optical bistable switching and triode operation using LiNbO3directional coupler

Optical bistable switching and optical triode operation have been carried out using an optical directional coupler switch fabricated by Ti diffusion into LiNbO3at the 1.15 μm wavelength. The on/off ratio in conventional bistable switching was 10 dB and that in complementary bistable switching was 13 dB. Amplification gain in triode operation controlled by laser diode was 4.8 dB. Complementary operation was found to reduce feedback gain and to improve the on/off ratio in optical bistable switching.     

Optical tristable device by vertical and direct integration ofheterojunction phototransistors and laser diodes

A light-controlled optical tristable device with an optical gain is actualized. The device has a configuration of vertical and direct integration of two heterojunction phototransistors (HPTs) on a laser diode (LD) along the cavity direction. An external optical input causes a bistable operation in one HPT+LD part. With the optical connection between two HPTs through the LD stripe, a bistable operation also occurs in the other HPT+LD part. The light-controlled optical tristability is achieved with the combination of the bistable operation in each HPT+LD part     

Optical spectral bistability in a semiconductor fiber ring laserthrough gain saturation in an SOA

We demonstrate the operation of optical bistability in a widely tunable semiconductor fiber ring laser, using a semiconductor optical amplifier (SOA). The laser can be operated in two bistable states: the spectrum of the first state has one main lasing peak with very narrow linewidth, and the second state has simultaneous oscillation of two main peaks at different wavelengths. The two bistable states can be switched to each other using either electrical or optical methods. We further explain the bistable operation using the theory of two-mode competition through gain saturation in the SOA     

Intermodal stability of a coupled-cavity semiconductor laser

We present an analysis of the steady-state operation of a two-element coupled-cavity laser near a mode hop. The equations of motion for the two cavities and two relevant modes of a longitudinally coupled-cavity laser are reduced to a system of nondimensional nonlinear ordinary differential equations which describe a general two-element laser. The equations are then solved and the stability of their solutions is analyzed. Depending upon the fill factors for the two modes, there exists an intrinsically multimode oscillation for operating conditions under which it was previously thought that no steady state existed. Under conditions where the multimode state is unstable, both of the single-mode states are stable with bistable transitions occurring only on the boundaries of the unstable multimode regimes.     

Self-pulsation in multielectrode distributed feedback lasers

Measurements on multielectrode distributed feedback (DFB) lasers without a saturable absorber reveal the existence of a self-pulsation (SP) regime. In this regime, the laser remains in the same single-longitudinal mode with simultaneous intensity and frequency modulation. The laser spectrum is similar to that of a current-modulated single-mode laser. At the up-limit of the SP regime, the behavior between the output power and the injection current becomes bistable. In one branch of the bistable loop, the SP laser presents a very large spectrum without distinguishable peaks, a kind of chaotic state with coherence collapse. A qualitative explanation based on the effective differential gain is given for the origin of SP and associated phenomena in these lasers