采用纵模匹配技术的短脉冲注入锁定染料激光器

本文报道了采用纵模匹配技术的短脉冲注入锁定染料激光器系统及实验结果.     

无纵模匹配注入锁定短脉冲染料激光器

本文报道了没有纵模匹配的注入锁定短脉冲染料激光器.实验结果表明,该激光器系统具有波长连续可调谐,脉冲短,输出线宽窄,功率高等特点.     

种子注入式单纵单横电光调Q激光器

基于种子注入技术、干涉法腔模锁定方案以及自滤波非稳腔技术,设计并研制出一套单纵单横电光调Q脉冲激光器系统。该系统输出的基波(波长1064nm)能量达到600mJ,倍频后绿光能量达到300mJ,发散角接近衍射极限,线宽接近傅里叶变换极限,在强气流强振动环境中单纵模的锁定概率为100%。实验观测了种子注入对巨脉冲建立时间、光斑模式以及能量的影响。该系统可应用于受激布里渊散射(SBS)、大视场风洞全息以及光学合成孔径等研究领域。     

注入锁定掺铒光纤环形腔激光器及波长调谐技术

研究了掺铒光纤环形腔激光器(EDFRL)的注入锁定现象,提出了一种实现可调谐的单纵模EDFRL波长及功率稳定的新方法,即利用注入锁定技术向法布里-珀罗可调滤波器结合复合腔结构的EDFRL腔内注入低功率的连续光,使某一纵模在注入连续光的基础上起振.这个纵模在对增益介质的竞争中可以稳定地占据优势,从而与注入信号发生锁定,实现激光器输出光谱的稳定.实验得到激光器在1527.4～1561.9 nm范围内波长可调,输出功率＞0.6 dBm,信噪比(SNR)＞43 dB;输出光波长与功率抖动分别＜0.01 nm和≤0.02 dB,且线宽约为1.4 kHz.     

注入锁定掺铒光纤环形腔激光器及波长调谐技术

研究了掺铒光纤环形腔激光器(EDFRL)的注入锁定现象,提出了一种实现可调谐的单纵模EDFRL波长及功率稳定的新方法,即利用注入锁定技术向法布里-珀罗可调滤波器结合复合腔结构的EDFRL腔内注入低功率的连续光,使某一纵模在注入连续光的基础上起振.这个纵模在对增益介质的竞争中可以稳定地占据优势,从而与注入信号发生锁定,实现激光器输出光谱的稳定.实验得到激光器在1527.4～1561.9 nm范围内波长可调,输出功率＞0.6 dBm,信噪比(SNR)＞43 dB;输出光波长与功率抖动分别＜0.01 nm和≤0.02 dB,且线宽约为1.4 kHz.     

抑制Nd:YAG激光器自锁模的实验研究

用于抽运钛宝石的电光调Q Nd:YAG激光器会出现自锁模调制,导致峰值功率不稳从而损伤钛宝石晶体,为了抑制这种自锁模调制,分析了产生该现象的原因,研究了谐振腔内插入法布里-珀罗(F-P)标准具的技术方案。实验采用单个厚度20mm,膜层反射率60%的标准具,有效抑制了该Nd:YAG激光器的自锁模调制,实现了脉宽约70ns,脉冲能量约600mJ的1064nm激光的稳定输出,既避免了引入较大的插入损耗,又防止了对F-P标准具膜层的损伤。分析认为单个厚度合适、膜层反射率不太高的标准具可有效抑制Nd:YAG激光器自锁模现象的原因在于:标准具一个透射峰半峰全宽(FWHM)内理论上虽有约5个纵模,但偏离透射峰中心的纵模损耗较大,使得单个透射峰内实际起振的纵模可能只有1个;激光器的增益线宽内虽存在标准具的多个透射峰,但起振纵模因不相邻避免了形成相位锁定。     

短脉冲注入锁定染料激光器的理论

本文提出了包含主激光器注入光频率与受迫激光器纵模频率之间失谐影响的新的速率方程模型,并给出了数值解. 注入功率、注入波长和频率先谐等因素对短脉冲注入锁定染料激光器的影响也进行了讨论.     

主动锁模光纤激光器的锁相稳定方法

对主动锁模光纤激光器的锁相环路进行了改进,提出一种通过使用"变带宽锁相环"来改善主动锁模光纤激光器稳定性的方法.该方法主要依据信号误差电压实时控制环路的带宽,使环路带宽随锁定信号的频率差动态改变,以达到快速锁定信号的目的,从而提高锁模光纤激光器输出光脉冲的频率稳定性.利用Matlab软件的Simulink功能模块对其实效性进行了仿真验证.结果表明,采用该方法,锁相环的捕捉性能和跟踪性能提高了,主动锁模光纤激光器的工作稳定性得到进一步改善.     

半导体激光器的纵模竞争分析

在(AlGa)As激光器)及1.3μm、1.5μmInGaAsP/Inp~2)激光器中,观察到纵模竞争的滞后现象。这种滞后现象揭示了在纵模中存在着“强耦合”。朗伯在论述气体激光器)时首先叙述这个问题。用他的关于带-带跃迁扰动方程的推广可直截了当地说明这种滞后现象。近来发现由于模跳跃而产生大的强度起伏,在半导体激光器的实际应用中出现     

重复频率脉冲激光纵模测量方法研究

提出了一种利用共焦球面扫描干涉仪对重复频率脉冲激光纵模结构进行测量的实验方法.该方法不仅能检测激光器是在单纵模还是多纵模下工作、计算待测激光的纵模间隔和谱线宽度,还能直接观测到各纵模的相对能量分布,测量精度高,结果直观,设备简单.实现了对1kHz以上重复频率脉冲激光纵模结构的测量,示波器上波形清晰稳定.利用该方法测量脉冲激光纵模结构在国内外文献中未见报道.     

Single axial mode operation of aQ-switched Nd:YAG oscillator by injection seeding

We have achieved stable Fourier transform limited single axial mode operation of an unstable resonator Nd:YAG oscillator by injection seeding of an external signal. A detailed theoretical and experimental treatment of axial mode selection via injection seeding is presented. Our study shows that the axial mode selection process inQ-switched lasers via injection seeding is quite different from the frequency locking in CW lasers via injection locking.     

CO2laser mode locking produced by sinusoidal cavity-length modulation

Mode locking of a CO2laser through the use of cavity-length modulation is reported. A cavity end reflector was sinusoidally modulated along the cavity axis at a frequency equal to the quiescent axial mode interval. Phase-locked pulsing occurred at a rate equal to or twice the axial mode interval.     

Structure dependent axial mode stability in GaAlAs/GaAs injection lasers

The influence of structure on the saturation behaviour of mode gain and the axial mode stability is investigated for different types of AlGaAs injection lasers. Both experimental and theoretical results confirm that carrier confinement along the lateral direction is effective for axial mode stabilisation.     

Effect of noise on active mode locking of a diode laser

Mode locking of semiconductor lasers as influenced by spontaneous emission is investigated. The magnitude of the spontaneous emission is determined from the number of axial modes above the half-power level of the free-running diode below and near threshold. A formula is developed which relates this noise source to that of the diode in an external resonator. It is shown that, without bandwidth limiting, the noise is large enough to impede mode locking. The SHG trace of a diode with no antireflection coating, mode locked in an external resonator, is predicted and compared with experiment.     

Coaxial-feed axial mode hemispherical helical antenna

A coaxial-feed axial mode hemispherical helical antenna is studied experimentally and theoretically. Results for a 3-turn hemispherical helix indicate that circular polarisation can be obtained over a broad beamwidth. The gain bandwidth is ~33% and the peak gain is 7.6 dB. The input impedance shows that it is a standing wave antenna     

Effect of waveguiding properties on the axial mode competition in stripe-geometry semiconductor lasers

Based on the multimode rate equations taking account of transverse mode and carrier density distributions, the axial mode behavior in semiconductor lasers is investigated. The axial mode stability is significantly affected by these distributions. Above threshold, because of hole burning in the carrier density distribution, the gain at any wavelength except the lasing wavelength does not maintain the value at threshold. If the nonlasing mode wavelength is located in the gain decreasing spectral region, its light output decreases with the increase of current. These characteristics are observed in the experiment for a CSP laser. For axial mode stabilization, a large built-in refractive index step is effective so long as single transverse mode operation is maintained. If the injection current region is defined separately from the guiding region, the wider width of the injection current region leads to a more stabilized axial mode.     

带异形反射腔和寄生螺旋的均匀升角轴向模螺旋天线

为了改善轴向模螺旋天线的辐射特性,在带有寄生螺旋的均匀升角轴向模螺旋天线基础上,设计了一种带有曲反射面背腔的螺旋天线,并用HFSS软件对天线的辐射特性进行了仿真分析。通过对比几种不同形式的螺旋天线的仿真结果,证明了该种螺旋天线可以有效地提高轴向模螺旋天线增益系数,圆极化一致性良好,是一种提高轴向模螺旋天线性能的有效方法。     

Active mode locking of broadband quantum cascade lasers

Active mode locking in broadband quantum cascade (QC) lasers with a repetition rate of about 14.3 GHz has been achieved through the modulation of the laser bias current. At low driving currents, the active mode locking in broadband QC lasers resembles the active mode locking in single-wavelength QC lasers, while at high driving currents, the mode locking properties are governed by the broad spectral gain of these lasers. At high bias currents, the active modulation excites Fabry-Perot modes across the entire gain spectrum from 6.7 to 7.4 /spl mu/m, with clear evidence of mode locking. The spectral width of the optical gain in the broadband QC lasers exceeds 2 THz and indicates the potential for generating subpicosecond pulses.     

Accordion shape monofilar axial mode helix for RFID reader

An accordion shape monofilar axial mode helical antenna designed by curving the helix along the axis is proposed. This antenna achieves a low-profile characteristic as the 10-turn helix's axial length is 0.354/spl lambda/. The impedance bandwidth (SWR<1.5) is 9% from the frequency of 880 to 963 MHz and the axial ratio bandwidth (AR<3 dB) is 6.5%. The measured gain is 10.2 dBi. This antenna operated at the centre frequency of 915 MHz and has a tilted radiation of 17/spl deg/ to the curving side.     

Harmonic mode locking of the Nd:YAG laser

We present experimental and theoretical results forNth harmonic mode locking of a Nd:YAG laser with an intracavity phase modulator operating atN = 2, 3, 4,and 5 times the fundamentalc/2Lfrequency. The bandwidths of the resulting mode-locked spectra depend upon modulation frequency, modulation depth, and laser cavity losses in good agreement with the Gaussian-pulse analysis of Kuizenga and Siegman [5]. For modulation atN(c/2L)the resulting pulse-repetition frequency is alsoN(c/2L)in all cases. However, in theN = 2case, for example, the mode-locked optical spectrum includes every adjacent axial mode component if the laser rod is located near the center of the laser cavity, but only every other axial mode when the rod is located at the end of the laser cavity. This behavior is explained by a Lamb-type theoretical analysis taking into account the competition between the two "hypermodes," or sets of interleaved next-adjacent axial modes, that can oscillate separately or simultaneously in theN = 2case.