Measurements on competition between carrier-induced and thermally-induced wavelength tuning in ridge waveguide DBR lasers

The tuning characteristics of ridge waveguide DBR lasers have been measured under CW and pulsed grating currents. Under CW grating current injection, a maximum tuning range of 2.5 nm was measured. This tuning range was extended to almost 7 nm under pulsed conditions. The increase in the tuning range is explained by the absence of thermal tuning mechanisms for pulsed grating currents and the dominance of thermal tuning in the ridge waveguide structure at large CW grating currents is explicitly shown.<>     

Tunable twin-guide distributed feedback laser diodes with over 9 nm continuous electro-optic tuning range

Tunable twin-guide laser diodes at 1.55 /spl mu/m with a record electro-optic tuning range are presented. Employing an optimised device design, continuous tuning ranges of 9.3 and 11.0 nm are achieved in continuous-wave (CW) and pulsed operation, respectively. In CW operation, the output power of 300 /spl mu/m-long devices remains above 1 mW throughout the whole tuning range.     

Multiple-phase shift super structure grating DBR lasers for broadwavelength tuning

Broad range wavelength tuning in distributed Bragg reflector (DBR) lasers using a super structure grating with multiple phase shifts is discussed. Experimental results indicate that the laser achieves a maximum tuning range of 105 nm with stable single-mode continuous wave (CW) operation     

Over 1100 nm wavelength tuning in superstructure grating (SSG) DBR lasers

A broad range tuning of over 100 nm in tunable DBR lasers with superstructure grating (SSG) is reported. The SSG reflectors for 100 nm were designed and patterned by electron beam lithography. 1.55 mu m DBR lasers with SSG reflector operate in a single mode with a tuning range of 83 nm under CW conditions. With inclusion of the multimode operating region, the tuning range becomes as wide as 103 nm.<>     

Short wavelength (/spl lambda//spl sim/4.3 /spl mu/m) high-performance continuous-wave quantum-cascade lasers

We report continuous-wave (CW) operation of a 4.3-/spl mu/m quantum-cascade laser from 80 K to 313 K. For a high-reflectivity-coated 11-/spl mu/m-wide and 4-mm-long laser, CW output powers of 1.34 W at 80 K and 26 mW at 313 K are achieved. At 298 K, the CW threshold current density of 1.5 kA/cm/sup 2/ is observed with a CW output power of 166 mW and maximum wall-plug efficiency of 1.47%. The CW emission wavelength varies from 4.15 /spl mu/m at 80 K to 4.34 /spl mu/m at 298 K, corresponding to a temperature-tuning rate of 0.87 nm/K. The beam full-width at half-maximum values for the parallel and the perpendicular far-field patterns are 26/spl deg/ and 49/spl deg/ in CW mode, respectively.     

Broad-range wavelength tuning in DBR lasers with super structuregrating (SSG)

Broad-range wavelength tuning is demonstrated in tunable distributed Bragg reflector (DBR) lasers with the super structure grating (SSG) proposed. The SSG is fabricated by electron beam exposure lithography. The grating performance is measured by transmittance characteristics of the SSG reflector. A maximum tuning range of 63 nm is obtained under the CW condition while keeping a single longitudinal mode. In a 50-nm tuning range, the threshold current variation is as low as 5.0-9.5 mA     

Tuning of mid-infrared diode lasers for spectroscopy operated insub-μs-pulses

Near room temperature operation and hence Peltier cooling for lead chalcogenide diode lasers can be achieved by using sub-μs-pulses. At present, the typical CW low operation temperatures of these lasers limit their commercial gas analysis applications. We experimentally investigated the spectral characteristics concerning tuning width, temporal and current tuning rate, and mode behaviour of short pulsed diode lasers. For understanding of the pulse tuning, we present a qualitative thermodynamic model calculation. We observed for the first time a temporary negative tuning, that is opposite to the common mechanisms of temperature and current tuning     

LNA: A new CW Nd laser tunable around 1.05 and 1.08 µm

We have investigated the CW laser properties of the lanthamide hexa-aluminate La0.9Nd0.1MgAl11O19at room temperature. When a 1 cm long crystal is pumped by an Ar+ laser (514 nm) or a Kr+ laser (752 nm), CW emission is obtained with slope efficiencies of 10 and 26 percent, respectively. A four-plate Lyot filter in the cavity forces the LNA crystal to oscillate in either of the two major bands centered al 10 820 Å (tuning range 80 Å) and 10 545 Å (tuning range 35 Å).     

可调谐微微秒染料激光脉冲宽度的二次谐波相关测量

本文讨论了二次谐波相关测量方案,并对Rh6G环形染料激光器的主动锁模和被动锁模脉冲宽度作了二次谐波相关测量。     

A frequency-tunable mode-locked CW Nd:Glass laser

Mode locking and frequency tuning of a CW light-focusing Nd : glass laser called the SELFOC Nd : glass laser were achieved. Using an acoustooptic modulator having a modest degree of modulation (about 3 percent), almost perfectly mode-locked pulses as short as 49 ps were obtained. Pulsewidth was measured with an intensity-correlation method using the second-harmonic generation in KDP. Most of the observed shapes of the intensity-correlation curves were in agreement with theories previously presented by several authors. When the laser was mode locked, the long-term averaged optical spectrum was observed to narrow considerably. Some experimental evidence that the CW SELFOC Nd:glass laser could be considered to have a homogeneously broadened line was also found. Frequency tuning was achieved by using a tilted etalon in a cavity. When a 50-μm-thick etalon was used, the tuning range was more than 40 Å. Pulses obtained from a frequency-tuned mode-locked laser were as short as about 100 ps.     

导频测量法--CDMA网络中传播模型校正的有效方法

校正移动通信的传播模型常用CW测试法，但因CW测试中有关测试点的选择、设备的架设等受诸多因素的影响，导致测试点数有限，同时人力、物力耗费较大。作者经过实际的测试摸索，提出了基于CDMA现网的导频测量法，大大提高了校正后传播模型的准确性，节省了人力和物力。     

The Design of the 394.6 Ghz Continuously Tunable Coaxial Gyrotron for DNP Spectroscopy

Results of the numerical investigations of the coaxial-cavity gyrotron with smooth frequency tuning are presented. The tuning is achieved by moving an internal cone-shaped rod along the device axis, which ensures smooth variations in eigenfrequencies of the cavity. The application of an inner conductor with an impedance surface reduces the thermal load on the internal road. The calculation results demonstrate the possibility of tuning the oscillator frequency by 8 GHz for the 394.6 GHz central frequency (within a frequency band of about 2%) with an output power of about several hundreds watts in the CW regime.     

Top-emitting micromechanical VCSEL with a 31.6-nm tuning range

We report a top-emitting micromechanical vertical-cavity surface-emitting laser (VCSEL) with a continuously tunable wavelength range of 31.6 nm, the widest tuning range demonstrated by a VCSEL to date. Good laser characteristics are maintained throughout the tuning range centered at 935 nm: continuous-wave (CW) threshold occurs between 1.24.5 mA while output power at 10-mA DC bias remains between 0.5 and 1.6 mW. By analyzing the pulsed differential quantum efficiency as a function of emission wavelength, we conclude that tilt loss from the cantilever design does not significantly affect the tuning range or laser performance     

Tunable single-frequency Yb:YAG laser with 1-W output power usingtwisted-mode technique

A diode-pumped, single-frequency Yb:YAG laser with >1-W CW output power has been demonstrated. Single-frequency operation is induced by using the twisted-mode technique, and an etalon has also been inserted into the cavity for timing. Single-frequency tuning from 1.02898-1.03174 μm has been achieved with a 116-μm-thick etalon; the tuning range was limited by the etalon's free spectral range     

Efficient phase-matched second-harmonic generation and sum-frequency mixing in urea

The performance of urea as a new nonlinear optical crystal for phase-matched second-harmonic generation and sum-frequency mixing in the UV is reported. Tunable radiation down to 229 nm was obtained. In particular, efficient doubling at room temperature of CW argon laser lines from 488 to 528 nm was achieved. The nonlinear coefficient of urea was measured and found to be 2.5 times that of ADP. Angle tuning curves for type II SHG, several type II frequency mixing schemes, temperature tuning data, and comparison to other nonlinear materials are presented. More accurate Sellmeier constants were also obtained using the measured angle tuning curve for type I SHG.     

基于TD-SCDMA系统的传播模型校正的研究

为了提高路径损耗预测的准确性,提出一种快速且精确的传播模型校正方法.该方法基于最小二乘理论,在现有校正方法和本地连续波(CW)实测数据的基础上对本地标准宏蜂窝传播模型进行校正.仿真结果表明,该方法的计算复杂性明显减少,且校正后的模型最大预测错误率减少20.5%,与本地无线传播环境更加匹配.     

Metal clad Pb1-xSnx Se/Pb1-x-yEuy SnxSe distributed feedback lasers

Distributed-feedback Pb_1-xSn_xSe double heterostructure stripe geometry diode lasers fabricated using molecular-beam epitaxy are discussed. These lasers operate in the CW mode up to 90 K and in the pulse mode up to 100 K. They are unique in their low tuning rate with injection current 4 cm^-1/A, and in that they withstand high CW injection currents without damage. These features are probably the result of the metal cladding layer located on top of the gratings     

Frequency modulation of Gunn-effect oscillators

Electronic tuning in CW X-band Gunn effect oscillators is reported. Several mechanisms which may account for the effects observed are discussed and discounted on the basis of simple models. An explanation in terms of growing domains is proposed.     

WCDMA无线传播模型校正与分析

准确的无线传播模型是WCDMA无线网络规划的基础.文章给出了传播模型CW测试校准要点和数据处理的有效方法,并从理论和工程实测两方面分析了在不同无线传播环境下WCDMA传播模型参数与无线传播环境的关系,从而确保所校正模型的合理性和准确性.     

Broad-band wavelength tunable picosecond pulses from CW passivelymode-locked two-section multiple quantum-well lasers

Wavelength tunable CW (continuous-wave) passive mode-locking of a two-section quantum-well laser coupled to an external cavity is demonstrated. A tuning range of 26 nm is achieved with typical autocorrelation full widths at half maximum of 4.5 ps. The pulses are not transform limited, having a typical time-bandwidth product of 2.5