Tuning fidelity of acoustooptically controlled external-cavitysemiconductor lasers

External cavity semiconductor lasers in extended- and ring-cavity configurations were tuned with chirp-compensating pairs of acoustooptic filters. Nanometer-size tuning gaps observed by previous workers were eliminated. The tuning range was approximately 80 nm for the extended cavity and at least 55 nm for the ring cavity. The root-mean-square tuning error was 0.036 nm for the extended cavity and 0.018 nm for the ring cavity. The output could be swept up to 35 mm in as little as 10 msec, limited by the radio-frequency generator. Transmittance measurements made on spare acoustooptic filters using the extended-cavity laser as a swept source were in good agreement with quasi-static measurements made using a grating-tuned laser     

外腔半导体激光器动态模稳定性的研究

为了研究调谐过程中外腔半导体激光器的模稳定性,采用多光束干涉理论推导Littrow结构外腔半导体激光器的腔增益,并模拟其模结构。分析了光栅面和转臂不在同一平面的情形下,在光栅转动调谐时,通过匹配光栅的反馈波长变化率与外腔波长变化率,推导出最佳的初始外腔长度,并研究了动态模稳定（无跳模调谐）的范围;采用严格的耦合理论和光线变换矩阵分析了准直（耦合）透镜的位置对系统后向耦合效率的影响。结果表明,系统后向耦合效率最大可达99%,极大地压窄了中心波长为780nm半导体激光器的线宽,外腔半导体激光器的理论线宽为未加外腔时的0.96%,动态模稳定范围可达6.8nm。     

Mode-Hop-Free, Optical Frequency Tunable 40-GHz Mode-Locked Fiber Laser

We have successfully achieved a mode-hop-free, optical frequency tunable 3-ps 40-GHz mode-locked fiber laser by installing an optical etalon in a 6.8-m laser cavity. The laser frequency was continuously tuned over 1 GHz without mode hopping by tuning the etalon peak frequency. The oscillation wavelength was also tuned over 1535-1560 nm by tuning an optical bandpass filter installed in the laser cavity.     

Continuously tuned external cavity semiconductor laser

Continuous tuning (no mode hops) of a grating-tuned external-cavity semiconductor laser by rotation of the grating about a carefully selected point is analyzed and demonstrated using a laser containing a prism beam expander. The analysis predicts the continuous tuning range as a function of pivot-point position and is used to select the point for maximum continuous tuning range. Because dispersive optical elements in the cavity were found to limit the continuous tuning range, the model was modified to include dispersion to first order. The dispersion correction improved the maximum observed tuning range of the 1300-nm-wavelength laser from 600 GHz to nearly 3000 GHz. Details of the cavity and mechanical design as well as pivot-point tolerances are also included     

A Stabilized MIC Oscillator Using a Germanium Avalanche Diode (Short Papers)

A stabilized X-band oscillator using a germanium avalanche diode in a microwave integrated circuit (MIC) is proposed. The stabilization is achieved by coupling a transmission cavity to the resonant cavity in which an avalanche diode is embedded. A mode-jumping problem inherent in a coupled-cavity oscillator was solved coupling a third varactor-embedded low-Q cavity to the transmission cavity. As a result, single-mode oscillation in an MIC oscillater was successfully obtained. Varactor tuning can also be realized with as small a change in output power as 7 percent for a tuning range of 30 MHz. The experimental results and the theoretical analysis of the new stabilized oscillator are given.     

掠射光栅复合腔调频

本文介绍一种结合了掠射光栅扩束及复合腔式谐振腔优点的脉冲染料激光系统。输出线宽可小于0.1孟,调频范围可达500且以上,调频效率超过30％,与单独掠射光栅调频腔相比,输出功率可提高几倍。     

电控宽带连续调谐外腔半导体激光器

介绍了一种电控调谐的外腔半导体激光器，并对其连续调谐特性进行了理论和实验分析。压电陶瓷（ＰＺＴ）（双晶片）的电扫描角度可达１°，采用适当的外腔结构，靠ＰＺＴ可同时改变外腔腔长和光栅衍射角，实现输出波长的调谐。该器件调谐范围最大可达１５ｎｍ，连续调谐范围（无跳模）为５０ＧＨｚ     

1.35 GHz线性调频Nd:YVO4激光器

报道了808 nm连续半导体泵浦全固态Nd:YVO4线性调频激光器实验研究。利用优化谐振腔长度、腔内插入倾斜标准具，采用温度控制、机械减震和隔绝外部环境等稳频操作，实现了稳定的1 064 nm单频激光输出，最大输出功率140 mW。利用法柏干涉仪观察单频输出，并利用刀口法测量得到的基模高斯光束质量M2为1.05。在谐振腔内插入RTP电光晶体并连接外部高压电源，通过线性电光效应改变谐振腔长度以及改变标准具倾斜角度避免腔长调节过程中的模式跳频，实现了1.35 GHz的稳定线性调频激光输出。编程控制高压电源给RTP晶体施加幅值为2 200 V的锯齿波形电压，实现了频率20 Hz，平均输出功率为85 mW周期性的调频信号输出。     

Electrical tuning of semiconductor interferometric laser

A semiconductor laser with a Michelson interferometer type cavity was electrically tuned by pumping each of its two branches separately. Two tuning modes were observed, small continuous tuning over 2.5 to 3 ? and step tuning with a total shift of 34 ?.     

Design and fabrication of GaAs-GaAlAs micromachined tunable filter with thermal strain control

In this paper, we present the design and fabrication of a novel GaAlAs-GaAs micromachined vertical cavity filter with a thermal strain control layer for wide wavelength tuning. The integration of a thermal strain control layer and heating element enables wavelength tuning induced by heating. The proposed tunable filter under thermal tuning operation provides us large tuning range over conventional micromachined tunable filters using electrostatic force. The calculated result shows a possibility of large continuous tuning range of over 100 nm. We fabricated a micromachined GaAlAs-GaAs vertical cavity filter with a strain control layer. The temperature dependence of the filter can be freely controlled either with temperature insensitive operation or with an enhanced temperature dependence, which depends on the thickness of the thermal strain control layer. We demonstrate a thermal wavelength tuning of 53 nm with a low tuning voltage of 6.1 V for the first time.     

Tuning characteristics of a tunable-single-frequencyexternal-cavity laser

The lasing characteristics of a tunable-single-frequency laser operated in conjunction with a tunable external cavity are investigated. The effect of phase error in the external cavity on the lasing frequency, linewidth, and output power is calculated by deriving the characteristic equation for the FP cavity as a traveling amplifier with an effective mirror concept. The analysis suggests that the diode laser and the external cavity may be successfully tuned open-loop if the feedback strength is appropriate and the tuning nonlinearities in the active and passive cavities are not too severe. This is demonstrated by maintaining a linewidth of 4 MHz while tuning continuously over 34 GHz     

Design and demonstration of a klystron with 62 percent efficiency

Extensive design optimization studies on a prototype series of klystrons have been carried out using a digital computer simulation, Five parameters were investigated for their effect on efficiency: 1) penultimate cavity tuning; 2) pre-penultimate cavity tuning; 3) beam perveance; 4) pre-pre-penultimate cavity tuning; and 5) output gap transit angle, These studies indicate that the power conversion efficiency of a high-power narrow-band multicavity klystron of optimum design should lie in the 70-80 percent range. A tube of near-optimum design was built and its performance was carefully measured as a function of two parameters: 1) penultimate and pre-penultimate cavity tuning; and 2) beam voltage. The measured data were used as a guide to determine the choice of beamfilling factor and beam power interception for best correlation with computed results. The measured efficiency was 62±1.5 percent compared to the computed value of 64 percent. Careful attention was paid to the repeatability of the efficiency measurements and to the effect of nonideal pulse shape on calorimetric measurements. Beam interception at large-signal levels appears to be the phenomenon which limits efficiency in the present tube.     

铌酸锂用于灯泵Cr-Tm:YAG激光器的调Q与调谐

为了简化激光器结构,减少腔内损耗,首次提出利用LiNbO3电光晶体较高的色散特性,实现2μm波段可调谐激光器的调Q与调谐。将LiNbO3晶体加工成单块特殊形状的棱镜,作为主动调Q器件,用于2μm波段灯泵Cr-Tm：YAG激光器,以产生巨脉冲,该棱镜还同时具有调谐的功能。将该棱镜插入室温灯泵的Cr-Tm：YAG激光器中,实现了1．95～2.08μm范围的调Q、调谐运转,重复频率为1-5Hz。实验结果表明,所提出的方法可行。     

Intermodal tuning behavior of an etalon-tuned three-mirror TEA CO2 laser

The detailed tuning behavior within a single ro-vibrational line of a TEA CO₂ laser was studied by using a wedged etalon and a pyroelectric array. The fine tuning of the laser was performed by using a temperature controlled etalon inside a three-mirror resonator. As the laser wavelength was scanned at a constant rate, single-longitudinal-mode pulses were observed ~82% of the time. Two-mode operation occurred over a narrow tuning range near the midpoint between successive cavity modes. The detailed structure of the staircase-like mode-to-mode tuning curve and the corresponding output intensity variations are explained using a simple theoretical model     

DBR单纵模光纤激光器波长温度调谐

报道了采用DBR方式,利用8 mm的高浓度掺Yb3+单模光纤,实现了波长为1 064 nm的单纵模调谐激光稳定输出的实验结果。该DBR谐振腔有效腔长为16 mm,输出最大功率为7.4 mW,通过半导体制冷器温控改变谐振腔的温度,实现了0.824 nm的单纵模无跳模调谐。采用光纤外差法,并利用低损耗环形器和光纤反射镜倍增延迟线长度提升测量精度的方式,测量得到激光最大线宽为4.4 kHz。单纵模激光的弛豫震荡峰位于900 kHz处,其相对强度噪声为-110 dB/Hz,当频率大于1.5 MHz时相对强度噪声为-145 dB/Hz。     

Investigation of tunable single frequency diode lasers for sensorapplications

The coherence and tuning properties of tunable single-frequencies lasers used in coherent detection systems have been investigated. The use of a fixed external cavity was found to increase significantly the coherence length of such systems but simultaneously reduce the tunability. An essentially all-electronic phase-modulated external cavity was used to restore the tunability, and a tuning range coherence length product of ~500 GHz-m was achieved. The modulated external activity laser was used in a coherent lidar system that achieved a maximum range of 150 m and a fractional resolution of 0.5%. The system is also shown to be a powerful tool for mapping out the tuning and coherence properties of tunable single-frequency lasers     

Some Notes on Strip Transmission Line and Waveguide Multiplexers (Comments)

Use of two tuning screws through the ground planes of a strip-line cavity resonator can excite the parallel plane TEM mode unless both screws are equidistant from the center conductor, rendering this method of tuning quite unattractive. A single tuning screw parallel to and midway between the ground planes is the better way of tuning a stripline cavity resonator.     

Micromirror device controlled tunable diode laser diode laser

An electronically controlled external cavity laser diode for fast wavelength tuning and multiple-colour lasing is presented. The spectral-tuning is accomplished by a digital micromirror device. Tuning of 47.4 nm with a tuning speed of 0.85 nm/ms was achieved. Simultaneous emission of up to 9 laser lines is demonstrated     

周期极化掺镁铌酸锂光参量振荡器的输出光谱特性

实验研究了基于多周期的掺镁铌酸锂晶体光参量振荡器(OPO),分析了光学参量振荡器的输出光谱特性.实验中,采用激光二极管(LD)端面抽运的声光调Q Nd:YVO4激光器作为光参量振荡器的抽运源,谐振腔采用双凹腔结构.在调Q开关重复频率为10 kHz,周期极化掺镁铌酸锂(PPMgLN)晶体的温度为25.4℃的条件下,实验测得光学参量振荡器的振荡阈值为110 mW.当输入的抽运光的平均功率为325 mW时,获得了平均功率为84 mW的信号光输出,其光-光转换效率为25.8%.通过改变周期极化掺镁铌酸锂晶体的温度(25.4～120℃)和极化周期(28.5～30.5 μm),实现了信号光在1449.6～1635 nm范围内的可调谐输出.在室温25.4℃时,观测到了抽运光与信号光的和频光的光谱.实验结果表明.光参量振荡器输出光谱的半峰全宽(FWHM)小于0.5 nm.     

Increased tuning range of Pb1-xSnxSe diode lasers using small magnetic fields

A Pb0.96Sn0.04Se laser diode emitting in the 815-835- cm^-1region with current tuning has been examined with applied magnetic fields at 7 kG and below. With increasing magnetic field the laser gain curve broadens, allowing more laser cavity modes (separated by 1.8 cm^-1) to oscillate at a given current, and yielding a larger tuning range with current for each cavity mode. Using a combination of current tuning and a constant magnetic field, laser emission was achieved from 800 to 850 cm^-1with 90 percent coverage of the spectral interval.