半导体多纵模激光器相干特性分析

本文运用傅立叶干涉分光计的原理和matlab工具 ,从半导体多纵模激光器的光谱图来分析其相干特性 ,指出其作为短相干光源的局限性 ,理论分析与实验结果基本一致。     

Chirping compensation using a two-section semiconductor laseramplifier

Compensation of light source chirping and optical fiber dispersion using semiconductor laser amplifiers (SLAs) is investigated using a modeling equation that describes the opposite phase characteristics of light sources to SLAs with self phase modulation. A two-section SLA was fabricated in order to achieve an amplifier with both high gain and phase compensation properties. Preliminary experimental results are presented, confirming the theoretically derived phase compensation effect     

Correlation between mode fluctuations in a multilongitudinal mode laser

A theoretical analysis of the correlation between mode fluctuations in a multilongitudinal mode laser is presented. The rate equations driven by Langevin noise sources are used to derive the correlation coefficients. By taking nonlinear terms into account, this analysis also applies to lasers with few modes and permits the derivation of the correlation coefficients from the the amplitude of these modes. They are found to be different from one pair of modes to another and to have not only negative, but also positive values. The fluctuations of a given mode are found to be concentrated in the low-frequency range, and the associated time constants are of great importance in the estimation of the partition noise for a signal propagating through a dispersive fiber.     

Spectral width reduction in multilongitudinal mode lasers byspatial loss profiling

Spatial loss profiling is experimentally and theoretically explored as a means of creating technologically useful reductions in the spectral width of multilongitudinal mode lasers. Lossy regions have been introduced at controlled locations along the optical axis of commercial laser diodes for the purpose of reducing the intensity of undesired longitudinal modes. Operation approaching single-mode characteristics with side-mode suppression better than 20 dB was experimentally achieved at 1.5X threshold current by the addition of three lossy regions. A rate equation model describes the effectiveness of spatial loss profiling to obtain quasi-single-mode operation and is used to explore its effects upon laser dynamics     

The performance of a traveling-wave-type semiconductor laseramplifier as a booster in multiwavelength simultaneousamplification

In this study, the theoretical worst and the average interchannel crosstalk are shown as a function of normalized input power. The validity of normalization by saturation input power is confirmed by experimental data. This normalized input power must be set below -20 and -10 dB for multiwavelength numbers of 20 and 4, respectively, to attain an average interchannel crosstalk of under -10 dB. The optical loss, including interchannel crosstalk, that can be compensated by a traveling-wave-type semiconductor laser amplifier (TWA) is analyzed. The experimental results indicate that the compensable optical loss could be evaluated by using the average interchannel crosstalk in multiwavelength transmission system design. Applying a TWA as a preamplifier is more effective in systems that include excess optical loss in the receiver     

Analysis of semiconductor diodes with multifrequency input signal

In this paper a closed form expression for the intermodulation output power from a semiconductor diode driven by an arbitrary number of "small-level" input signals is obtained. The effect of the intrinsic resistance of the diode material is taken into consideration through the use of the modified exponential function for the diode characteristic. It has been found that the relative harmonic distortion depends on the bias voltage, which agrees with the experimental observations. This dependence would not have been obtained had the intrinsic resistance been neglected. Also, the calculated intermodulation output power shows good agreement, for small input signal, with the published experimental results.     

Miniature packaged external-cavity semiconductor laser with 50 GHzcontinuous electrical tuning range

Miniature, packaged, grating-external-cavity lasers have been developed for use in PSK and DPSK coherent transmission systems at 1.5 μm. The outside dimensions of the package are 30×30×50 mm and the optical cavity length is nominally 30 mm, resulting in a spectral linewidth <100 kHz. The lasing wavelength is mechanically adjustable over the range 1510-1560 nm and electrically tunable over the range of 0.8 nm. With appropriate control of the grating piezos, a continuous (hop-free) tuning range of 50 GHz (0.4 nm) can be obtained     

Investigation of polarization dispersion in long lengths of single-mode fiber using multilongitudinal mode lasers

We have used multilongitudinal mode lasers to investigate the polarization properties of long lengths of single-mode fiber cable. We find that the individual longitudinal modes are >99-percent polarized after propagation through 54.6 km of cabled fiber; however, the different longitudinal modes have different states of polarization at the output. This difference is caused by polarization dispersion, and we estimate a propagation delay difference for the two principal states of polarization to be 0.42 ps in the 54.6 km of cabled fiber.     

Recovery of a π phase shift in ~12.5 ps in a semiconductor laseramplifier

Time-resolved interferometry is used to measure the relaxation of an optically induced phase change in a semiconductor laser amplifier (SLA). A phase change of π recovers in ~12.5 ps. This is proof-of-principle that an interferometric switch using an SLA can be gated at ~80 GHz     

Optical System with two packaged 1.5 ?m semiconductor laser amplifier repeaters

The first demonstration of two packaged 1.5 ?m semiconductor laser amplifiers in an optical system is reported. Total coupling losses for the fibre-tailed packages were 10dB and 13 dB, respectively. In a 140 Mbit/s intensity-modulated system experiment, using the amplifiers as linear repeaters, a total repeater again of 26 dB was achieved.     

Miniature packaged actively mode-locked semiconductor laser with tunable 20 ps transform limited pulses

Miniature, fibre tailed and packaged, wavelength tunable actively mode locked semiconductor lasers have been developed for use as sources of approximately 20 ps transform limited pulses. Continuous stable operation with >40 nm tuning ranges centred either at 1.3 mu m or 1.55 mu m have been demonstrated. The package has an adjustable cavity length enabling the repetition frequency to be selected between 2 GHz and 8 GHz. Mean output powers in the monomode fibre tail are in the range -10 dBm to -5 dBm.<>     

Electrooptic modulation of multilongitudinal mode laser diodes: Demonstration at 850 nm with simultaneous data transmission by coherence multiplexing

An electrooptic modulation method based on signal coding through optical delays larger than the source coherence length is described. The method is illustrated with the simultaneous transmission of several signals by path-difference multiplexing. In this method, the signals are coded as a sequence of optical delays introduced by a series of electrooptic modulators working as delay lines. Decoding is carried out by temporal correlation performed by another sequence of optical delays introduced by birefringent plates, and matched to those used at the emission process. The permissible delays are shown to be ruled by the source coherence length and by the number of laser modes.     

A new wide-band input compensation for packaged analog and digitalmultigigabit IC's

Packaging of multigigabit IC's introduces an input series inductance due to the bondwire which has a dominant influence on the overall IC performance. This paper describes the design and implementation of a novel input compensation circuit that both reduces the effects of the series inductance and offers the possibility to use an external termination with different impedances. Furthermore, a detailed theoretical investigation into the performance of the circuit is presented. A 7.4 Gb/s D-type flip-flop and a 4.2-GHz, 35-dB gain amplifier have been realized in a commercial 1-μm silicon bipolar IC process with an average f_T of 11 GHz, showing the good performance of the input circuit     

Current mode instrumentation amplifier with rail-to-rail input and output

This paper presents the results from an investigation on the implementation of Current Mode Instrumentation Amplifiers (CMIAs) with rail-to-rail operational amplifiers (op amp) with a gm control circuit. The objective of employing rail-to-rail op amps in the implementation of a CMIA is the improvement of the common-mode operation range. The enhancement of the input common mode range (ICMR) is obtained using op amps with a rail-to-rail input stage followed by a cascode-based output stage. A prototype of the CMIA was implemented in standard 0.6 μm XFAB CMOS technology. Test results showed that the CMIA common mode range was extended but with moderated CMRR. To minimize this issue the amplifier was re-designed and sent to fabrication. Simulations with the components variations included were performed and showed the enhancement of the CMRR can be expected.     

半导体激光器的输出模谱

利用半导体激光器多模速率方程组的隐式解析解，考虑到实际激光器的峰值增益波长与峰值谐振波长往往不一致的情况，从理论上对不同电流下半导体激光器的输出模谱进行了研究。     

Lateral mode dynamics of semiconductor lasers

The interaction between two lateral modes in a waveguide semiconductor laser is studied. The effects of carrier diffusion are included into the governing rate equations. A linear stability analysis is used to identify regions of frequency locking between the lateral modes. Numerical integration shows the effects of the diffusion length and other system parameters on the lateral mode dynamics. It is shown that variations in the carrier diffusion length give rise to regimes of single-mode dominance, oscillation, chaos, and frequency locking. Direct experimental observations of higher order lateral modes in lasers exhibiting beam instabilities are presented. Observations of bistable beam steering with hysteresis are presented and explained     

Analyses of mode partition and mode hopping in semiconductor lasers

Mode power fluctuations in semiconductors laser due to mode partition and mode hopping are discussed. The power dropout probability P_e in the mode partition was measured for a wide range, 1.6×10^-6⩽P_e⩽1, which decreased by increasing I/I_th (I and I_th are the DC injection current and its threshold value respectively). The duration time t_d of the power dropout expressed at t_d=3.7×10 ⁴⁸ exp[-118 (I/I_th)] for 1.065⩽I/I_th⩽1.104. Power fluctuations exhibited specific characteristics around the threshold, which were similar to the critical slowing down in the phase transition phenomenon. An increase in the variance of the power fluctuations was observed when the laser oscillating condition was converted from mode partition to mode hopping. The unified stochastic model based on the Fokker-Planck approach described well both mode partition and mode hopping     

Slab-coupled 1.3-μm semiconductor laser with single-spatiallarge-diameter mode

A high brightness semiconductor diode laser structure, which utilizes a slab-coupled optical waveguide region to achieve several potentially important advances in performance, is proposed and experimentally demonstrated using a simple rib waveguide in an InGaAsP-InP quantum-well structure operating at 1.3-μm wavelength. These lasers operate in a large low-aspect-ratio lowest-order spatial mode, which can be butt coupled to a single-mode fiber with high coupling efficiency