Broadly wavelength-tunable external cavity, mid-infrared quantumcascade lasers

Wavelength tuning over 120 nm for a grating-coupled 5.1-μm quantum-cascade type-I laser was studied for temperature from 80 to 243 K (-30°C). Both the Littman-Metcalf and first-order grating direct feedback cavity configurations were used with similar tuning results. The goal is to achieve broad tunability, and the result is a combined grating and temperature tuning of 245 nm, from 5.040 to 5.285 μm. The laser was designed for predominantly single-mode or at most, two-longitudinal mode operation. The instrument-limited laser linewidth was less than the cavity longitudinal mode spacing. Stepping-motor control of the grating allowed 0.4-GHz wavelength increments (35 pm) to be realized with high reproducibility. A current-induced wavelength shift of ~2-3 GHz was observed, corresponding to an effective refractive index change of ~10^-3. Analysis indicates that single-mode, continuously tunable operation is feasible with a more optimal device and cavity     

减反射膜与外腔半导体激光器调谐范围

由于镀了减反射膜的半导体激光二极管端面的反射曲线的谱宽有限，而且，增益峰值波长随载流子密度的变化，因而实际上起作用的反射率通常都比能测到的最低反射率高，在腔内可建立的载流子密度的上限比预期的低。在考虑了这些因素后，计算了用这种管子作外腔半导体激光器（ＥＣＬＤ）的增益介质时，ＥＣＬＤ的调谐范围。     

射线法研究外腔半导体激光器的调谐范围

利用由射线法导出的广义两段式半导体激光器的输出光谱的表达式，讨论了外腔式半导体激光器（ＥＣＬＤ）的调谐范围，当ＥＣＬＤ调谐到半导体激光二极管的共振波长附近振荡时，可以重到ＥＣＬＤ的最大调谐范围；当激光器调谐到半导体激光二极管的反共振波长附近振荡时，可以获得ＥＣＬＤ的准连续调谐范围；同时，还求得了实现准连续调谐所需的面向外腔的半导体二极管端面的反射率。     

长外腔半导体激光器的调谐连续性

可调谐外腔半导体激光器（ＥＣＬＤ）中的波长选择元件（如光栅，Ｆ－Ｐ标准具等）所选择的波长函数具有一定的频谱宽度，为实现连续调谐该宽度就应足够小，作为首次尝试，在研究了确保ＥＣＬＤ能在激光二极管的以共振长振荡所需的条件后，我们导出该谱宽不能超过的上限值。     

MQW wavelength-tunable DBR lasers with monolithically integrated external cavity electroabsorption modulators with low-driving voltages fabricated by selective-area MOCVD

The design and operation of multiple-quantum-well (MQW) wavelength-tunable distributed Bragg reflector (DBR) InGaAs QW lasers with nonabsorbing gratings and monolithically integrated external cavity electroabsorption modulators fabricated by selective-area MOCVD are presented. Uncoated devices exhibit CW threshold currents as low as 10.5 mA with slope efficiencies of 0.21 W/A from the laser facet. Wavelength tuning of 7 nm is obtained by injection current heating of the DBR section. These devices also exhibit extinction ratios of 18 dB from the modulator facet at a low modulator bias of 1 V, when measured with a broad-area detector. When coupled to a singlemode fiber, these devices exhibited high extinction ratios of 40 dB at a modulator bias of 1.25 V.     

实现外腔半导体激光器连续调谐的两个基本要求

定量讨论了实现外腔式半导体激光器连续调谐的两个基本要求:同时改变外腔长度及光栅反射波长,半导体激光器(LD)端面镀减反膜。分析表明:前人给出外腔的可调整范围并非是实现最大调谐范围的必要条件,而是实现调谐连续性的一种可行选择。针对具体的减反射膜,对在ECLD上可能实现的连续调谐范围进行了研究。     

10 kHz linewidth 1.5 ?m InGaAsP external cavity laser with 55 nm tuning range

An InGaAsP 1.5 ?m laser, with one facet antireflection coated, has been incorporated into a diffraction grating external cavity. The lasing wavelength could be tuned over a 55 nm range about the centre wavelength of 1.5 ?m by rotating the grating. Furthermore, it was found that the emission spectrum was extremely narrow; beat-frequency measurements at 1523 nm against an HeNe laser showed it to be of the order of 10 kHz.     

Low-threshold quantum dot lasers with 201 nm tuning range

A grating-coupled external-cavity quantum dot laser is tuned across a 201 nm range at a maximum bias of 2.87 kA/cm². One order of magnitude less than the bias required for comparable tuning of quantum well lasers. The tuning range increases for higher cavity losses of the quantum dot laser     

Continuously wavelength-tunable MQW fabry-perot laser diode pulse source with a fiber-based external cavity

A simple continuously wavelength-tunable fiber ring laser pulse source is demonstrated. Such a source employs a gain-switched multiple quantum-well Fabry-Perot laser diode in a self-seeding scheme and the output pulse wavelength can be tuned continuously via a tunable optical filter. The optical pulses generated exhibit a pulsewidth of 92 ps at the frequency of 2.6 GHz. Within a wide wavelength tuning range of 46 nm, the side-mode suppression ratio and the average power of the output optical pulses obtained are higher than 50.1 dB and 3.3 dBm, respectively, and the pulse spectral stability can be maintained in the whole wavelength tuning range.     

一种面向多标准无线收发器的低功耗宽调谐范围基带滤波器设计

本论文提出了一种面向多标准收发器的具有精确片上调谐电路的低功耗宽调谐范围基带滤波器。设计的滤波器是由三级Active-Gm-RC类型的双二次单元级联组成的六阶巴特沃斯低通滤波器。采用改进的线性化技术来提高低通滤波器的线性度。论文提出了一种新的匹配性能与工艺无关的跨导匹配电路和具有频率补偿的频率调谐电路来增加滤波器的频率响应精度。为了验证设计方法的有效性,采用标准的130nm CMOS工艺对滤波器电路进行流片。测试结果表明设计的低通滤波器带宽调谐范围为0.1MHz-25MHz,频率调谐误差小于2.68%。滤波器在1.2V的电源电压下,功耗为0.52mA到5.25mA,同时取得26.3dBm的带内输入三阶交调点。     

Broadly tunable InGaAsP/InP vertical-coupler filtered laser with low tuning current

A tuning range of 48 nm has been achieved with a tuning current of only 40 mA in a 1.55 mu m InGaAsP/InP multiquantum-well laser based on a grating-assisted vertical coupler intracavity filter. Using a combination of current and voltage tuning a 55 nm tuning range was demonstrated.<>     

600 MHz direct modulation of short external cavity wavelength-tunable diode laser

The current modulation characteristics of a short external cavity tunable laser are presented. The 1540 nm Fabry-Perot diode laser is wavelength-tuned by the electrostatically controlled silicon micromachined Fabry-Perot interferometer device. The measured -3 dB cutoff frequency of 600 MHz is the widest reported direct modulation bandwidth of the external cavity tunable laser.     

Broadly tunable external cavity laser diodes with staggered thickness multiple quantum wells

Widely tunable low-threshold current laser diodes fabricated from an engineered multiple-quantum-well (MQW) gain structure consisting of three compressively strained In/sub 0.2/Ga/sub 0.8/As wells of different thicknesses are reported. Using a grating in an external cavity, a continuous-wave tuning range of 70 nm (911-981 nm) is measured for a 155-/spl mu/m semiconductor cavity length device at a current of 32 mA. This is the lowest reported bias current for a semiconductor laser with this broad a tuning range. A maximum continuous wave tuning of 80 nm (901-981 nm) has been measured at a bias current of 95 mA. At long wavelengths, a suppression of amplified spontaneous emission and preferential population of the lowest energy well were observed.     

Extended tuning range in sampled grating DBR lasers

The authors demonstrate, for the first time, successful implementation of a distributed Bragg reflector laser with two sampled grating mirrors, which they previously predicted should give tuning range in excess of 50 nm. This device uses a uniform grating pitch throughout the structure, and relies on the same fabrication technology as a standard DBR laser. Initial results show 57 nm of mathematical tuning at 1.475 μm with side-mode suppression ratio (SMSR)>30 dB over much of the tuning range. The observed change in operating wavelength versus mirror currents along with below threshold spectra agree with theoretical expectations     

Ridge waveguide sampled grating DBR lasers with 22-nmquasi-continuous tuning range

We demonstrate a ridge waveguide sampled-grating distributed-feedback laser with continuous wavelength coverage over a 22-nm tuning range, the largest ever reported for a ridge waveguide structure. The design is based on a 400-nm-thick 1.4-μm bandgap waveguide optimized for carrier injection tuning with offset quantum wells used to form the active region. The offset quantum wells enabled the device to be fabricated with only a single metal-organic chemical vapor deposition regrowth step. By tuning both mirror sections and the phase control section we were able to obtain 27 wavelength-division-multiplexed channels spaced at 100 GHz and precisely centered on the ITU grid with equal output power and greater than 40 dB of sidemode suppression ratio     

Single-polarization wavelength-tunable fiber laser with anonreciprocal cavity

Unidirectional, continuously tunable, and polarized oscillation in an erbium doped fiber ring laser is demonstrated without an isolator. Nonreciprocal oscillation is realized with one polarization splitter and two polarization controllers. Fine tuning is realized with fiber birefringence. The laser spectrum is continuously tunable from 1530 to 1560 nm with line widths less than 0.2 nm; the degree of polarization at the output is 92%     

Transient effects in external cavity semiconductor lasers

In several important applications of external cavity operated semiconductor lasers, including studies for FM optical communication and frequency stabilized lasers for coherent communication systems, the transient response of the laser is of crucial importance. In this letter, we present a first study of the transient optical response following a step current excitation applied to an AlGaAs laser operating in a dispersive external cavity. The study shows for the first time that, for optical feedback near the gain peak of the laser, a steady state is reached after only three roundtrips in the external cavity. However, for optical feedback far (∼100 Å) from the gain peak, 20 or more roundtrips are required before a steady state can be reached. It is also shown that under certain operation conditions the optical feedback can induce damped relaxation oscillations at each subsequent roundtrip in the external cavity.     

外腔式He-Ne激光器的偏振特性

实验观察到外腔式He-Ne激光器由于增益管的应力双折射效应而呈现复杂的偏振特性.对几种典型的增益管的应力双折射相移进行了理论分析和实验测量.在增益管端口的增透片上施加适当的径向压力可获得单一的线偏振光输出.     

Microchip vertical external cavity surface emitting lasers

Monolithic vertical external cavity surface emitting lasers of cavity mode volume <1 mm/sup 3/ have been fabricated in the 850 and 980 nm wavelength range. Pump-limited output power >350 mW in a TEM/sub 00/ mode was obtained at 850 nm. Output power >2.5 W was obtained at 980 nm.     

Waveguide external cavity narrow linewidth semiconductor lasers

Narrow linewidth light source is a prerequisite for high-performance coherent optical communication and sensing.Waveguide-based external cavity narrow linewidth semiconductor lasers(WEC-NLSLs)have become a competitive and attractive candidate for many coherent applications due to their small size,volume,low energy consumption,low cost and the ability to integrate with other optical components.In this paper,we present an overview of WEC-NLSLs from their required technologies to the state-of-the-art progress.Moreover,we highlight the common problems occurring to current WEC-NLSLs and show the possible approaches to resolving the issues.Finally,we present the possible development directions for the next phase and hope this review will be beneficial to the advancements of WEC-NLSLs.