Widely frequency tunable amplified feedback laser as 20 GHz optical microwave source

Optical microwave sources are required in optical signal processing. Amplified feedback laser (AFL) which can generate high frequency self-pulsation due to compound cavity modes beating are used as optical microwave sources. In this paper, we fabricate a four-section AFL consisted of a different distribute feedback (DFB) section, a phase control section, an amplifier section, and a transparent section. This AFL generate continuously tunable microwave in the range 19.87–26.30 GHz with 3 dB linewidth about 3 MHz. Microwave with narrow linewidth is obtained by injecting quarter frequency modulated light experimentally.     

Stabilization of millimeter-wave frequencies from passivelymode-locked semiconductor lasers using an optoelectronic phase-lockedloop

The use of an optoelectronic phase-locked loop to stabilize the pulsation frequency of a three-section, passively mode-locked quantum well laser diode at 41 GHz is discussed. It is shown that the free-running mode-locked signal, with a radio frequency (RF) linewidth of 770 kHz, can be stabilized to the linewidth of a reference RF oscillator (<1 kHz). The stabilized mode-locked signal has a phase noise of -70 dBc/Hz at 370 kHz offset. Tracking of the mode-locked signal to the external reference RF oscillator is maintained over 11 MHz. This is, in effect, an actively mode-locked laser source at 41 GHz     

High-frequency pulsations in DFB lasers with amplified feedback

We describe the basic ideas behind the concept of distributed feedback (DFB) lasers with short optical feedback for the generation of high-frequency self-pulsations and show the theoretical background describing realized devices. It is predicted by theory that the self-pulsation frequency increases with increasing feedback strength. To provide evidence for this, we propose a novel device design which employs an amplifier section in the integrated feedback cavity of a DFB laser. We present results from numerical simulations and experiments. It has been shown experimentally that a continuous tuning of the self-pulsation frequency from 12 to 45 GHz can be adjusted via the control of the feedback strength. The numerical simulations, which are in good accordance with experimental investigations, give an explanation for a self-stabilizing effect of the self-pulsations due to the additional carrier dynamic in the integrated feedback cavity.     

Frequency and wavelength tunable optical microwave source based on a distributed Bragg reflector self-pulsation laser

A frequency and wavelength tunable self-pulsation laser based on DBR laser devices is reported for the first time.This laser generates continuous tunable optical microwave in the range of 1.87-21.81 GHz with 3-dB linewidth about 10 MHz by tuning the injection currents on the front and back gain sections,and exhibits wavelength tuning range from 1536.28 to 1538.73 nm by tuning the injection currents on the grating section.     

Dispersive self-Q-switching in self-pulsating DFB lasers

Self-pulsations reproducibly achieved in newly developed lasers with two distributed feedback sections and with an additional phase tuning section are investigated. The existence of the dispersive self-Q-switching mechanism for generating the high-frequency self-pulsations is verified experimentally for the first time. This effect is clearly distinguished from other possible self-pulsation mechanisms by detecting the single-mode type of the self-pulsation and the operation of one section near the transparency current density using it as a reflector with dispersive feedback. The operating conditions for generating this self-pulsation type are analyzed. It is revealed that the required critical detuning of the Bragg wavelengths of the two DFB sections is achieved by a combination of electronic wavelength tuning and current-induced heating. The previous reproducibility problems of self-pulsations in two-section DFB lasers operated at, in principle, suited current conditions are discussed, and the essential role of an electrical phase-control section for achieving reproducible device properties is pointed out. Furthermore, it is demonstrated that phase tuning can be used for extending the self-pulsation regime and for optimizing the frequency stability of the self-pulsation. Improved performance of the devices applied as optical clocks thus can be expected     

光泵亚毫米波激光器双稳自脉冲运转特性

研究了光泵亚毫米波激光器的双稳和自脉动等动力学行为.结果表明泵浦光能产生双稳效应,导致输出光的一部分定态不存在,脉动输出较易产生,脉动频率随着泵浦光强的增大而增大.     

Optical feedback stabilization of the intensity oscillations inultrahigh-frequency passively modelocked monolithic quantum-well lasers

The effect of optical feedback on the stability of the modelocking frequency of monolithic, passively modelocked semiconductor lasers at ~50 GHz is investigated. Optical feedback leads to linewidth narrowing, frequency pulling, and multiple modes of the intensity modulations in modelocked lasers, reminiscent of similar effects on the optical frequency in conventional continuous wave (CW) lasers. The narrowest observed line has a full-width-at-half-maximum (FWHM) of 56 kHz, which represents close to two orders of magnitude reduction of the linewidth compared to the situation without feedback. The effects of the optical feedback vary periodically as the length of the feedback delay is varied, with a periodicity that roughly matches the mode-locking wavelength. This wavelength is on the order of millimeters, which makes the mechanical stability of the optical feedback loop relatively uncritical     

FM noise and spectral linewidth reduction by incoherent opticalnegative feedback

An all-optical, stable, external feedback method, the incoherent optical negative feedback method, is proposed and demonstrated for spectral linewidth reduction and optical-frequency stabilization of distributed-feedback (DFB) lasers. The power-spectral density of frequency modulation (FM) noise is shown to be reduced in a wide range of up to several hundreds of megahertz. The linewidth and the optical-frequency drift are simultaneously experimentally reduced to about 140 kHz and less than 17 MHz, respectively. The frequency range of the effective FM noise reduction and the reduction ratio of the FM noise are up to 1 GHz and 22 dB, respectively     

Widely frequency-tunable amplified feedback lasers for 10-GHz optical pulsation

Monolithic amplified feedback semiconductor lasers are demonstrated as a new solution to 10-GHz optical pulsation, where self-pulsations are generated according to the concept of a single-mode laser with shortly delayed optical feedback. They consist of a loss-coupled distributed feedback section operating as a single-mode laser and an integrated feedback cavity including a phase control, an amplifier, and a transparency section. The pulsation frequency is continuously tunable in the range of 7-11.5 GHz with an extinction ratio above 6.5 dB, which indicates that precise control of a cavity length is not needed.     

An Ultralow Noise and Narrow Linewidth λ/4-Shifted DFB Er-Doped Fiber Laser With a Ring Cavity Configuration

We report a polarization-maintaining lambda/4-shifted distributed feedback (DFB) Er-doped fiber laser with a ring cavity configuration. The ring cavity suppressed the self-pulsation of the stand-alone Er-doped DFB fiber laser. The laser with a 57-m-long ring cavity achieved single-longitudinal-mode operation, a linewidth as narrow as 6 kHz, and relaxation-oscillation-free noise characteristics.     

Effects of intermodulation distortion on the performance of a hybrid radio/fiber system employing a self-pulsating laser diode transmitter

A self-pulsating laser is used to generate a multicarrier (five radio frequency (RF) channels) microwave optical signal for use in a hybrid radio/fiber system. The self-pulsation is achieved by external light injection into the laser diode. By varying the RF channel spacing, we have been able to estimate the degradation in system performance due to intermodulation distortion (caused by the nonlinear dynamic response of the laser). The power penalty on the central RF channel is found to be 3.2 dB for operation at the RF band around the laser self-pulsation frequency of 18.5 GHz. We have also characterized the performance of the multicarrier hybrid radio/fiber system in the frequency band corresponding to the inherent relaxation frequency of the laser.     

Optoelectronic oscillator employing reciprocating optical modulator for millimetre-wave generation

An optoelectronic oscillator that employs a reciprocating optical modulator is demonstrated. By giving positive optoelectronic feedback to the modulator, the reciprocating modulation in the modulator effectively multiplies the fundamental oscillation frequency by several times. A 52.8 GHz millimetre-wave signal is generated by self-oscillation.     

Observation of sustained self-pulsation in CW operated flaredY-coupled laser arrays

The time evolution of the near-field radiation patterns of CW operated inphase locked flared `Y' coupled diode laser arrays has been observed with a streak camera. The arrays exhibit sustained self-pulsation at frequencies as high as 4 GHz     

High-temperature operation of 650-nm wavelength AlGaInPself-pulsating laser diodes

Low-coherence self-pulsating laser diodes operating at a wavelength of 650 nm and at temperatures in excess of 70°C are required for high density optical storage systems. We report on AlGaInP lasers operating at this wavelength which exhibit stable self-pulsation up to a temperature of 100°C. The lasers are 50-μm-wide oxide-isolated stripe devices in which the saturable absorption necessary for pulsation is provided by multiple-quantum wells placed within the p-doped cladding layer. The pulsation frequency of the devices increases linearly with increasing drive current and is present up to 1.5 times, lasing threshold     

10MHz?4GHz 超宽带微波光电子系统设计

为了改善高频微波进行长距离传输时具有很大的损耗,频率向高频扩展受限的特性。本文基于微波信号光纤 传输 （RoF）技术,采用波长为1550nm 的多量子阱分布式反馈激光器和数据速率高达10Gbps 的数字式PIN 光电探测 器,设计了一款工作频率为10MHz~4GHz 的超宽带微波光电子系统。在整个频率范围内满足了8dB 增益,增益平坦度 ? 1.5dB 及输入/输出驻波比＜2 的指标要求,符合工程需要,实现了数字式光电子器件在模拟通信中的应用,具有广泛 的应用范围。     

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     

Wideband frequency-response measurement of optical receivers usingoptical heterodyne detection

Measurements have been carried out using 1.3-μm distributed-feedback laser diodes (DFB-LDs). The frequency difference of the LDs is continuously varied with temperature changes of a few degrees and the spectral linewidth of one of the LDs is narrowed by optical feedback using a grating. Wideband, highly sensitive measurement has been achieved for a p-i-n photodiode and a Ge avalanche photodiode from DC to 20 GHz. The result is compared with that of the pulse spectrum analysis (PSA) method. Although the finite pulsewidth in the PSA method causes roll-off in the frequency response, the optical heterodyne method has the advantage for very wideband frequency response measurement. The S/N ratio in the optical heterodyne method can be made as high (~40 dB) as that of the PSA method by narrowing the spectral linewidth of DFB-LDs     

Performance analysis and stability testing of a new structure of optoelectronic integrated device

This paper is devoted to the evaluation of the transient performance as well as testing the stability of a new version of optoelectronic integrated devices. This version is composed of a resonant cavity enhanced heterojunction phototransistor and a light-emitting diode. It will be called as a resonant cavity enhanced optoelectronic integrated device. The evaluation of its transient response is based on the frequency response of the constituent elements and the optical feedback inside the device. Analytical expressions describing the transient behavior are derived. The numerical results show that the transient performance of the version under consideration strongly depends on the optical feedback inside the device and it has a very high optical gain in comparison with the conventional types. In addition, the possibility of operating the new device in two distinct modes is also available as similar to conventional types. Moreover, testing the stability of the new version demonstrates that its optical gain is stable as long as the value of the optical feedback is maintained below threshold value, while exhibits instability for values of optical feedback, which is greater or equal to this threshold value.     

Optical frequency scanning of a stabilised and linewidth-reduced multielectrode DFB laser using current feedback

Optical frequency scanning of a stabilised and linewidth-reduced multielectrode DFB laser has been demonstrated using a current feedback technique. The scanning range of the linewidth-reduced multielectrode DFB laser was 4? (50 GHz) and 9? (120 GHz) when the linewidth was reduced to 1/50 and 1/20, respectively, of that of a free-running state laser.     

Self-Pulsating Amplified Feedback Laser Based on a Loss-Coupled DFB Laser

Monolithic self-pulsating semiconductor lasers called amplified feedback lasers (AFLs) can generate high-frequency self-pulsations according to the concept of a single-mode laser with shortly delayed optical feedback, which consist of a distributed-feedback (DFB) laser, a phase control, and an amplifier section. Since mode degeneracy of the DFB section, which should operate as a single-mode laser, affects the self-pulsation, single-mode characteristics of the DFB section are critical for the self-pulsation. The effect of a complex coupling in the DFB section on the self-pulsation is numerically analyzed to reveal that the complex coupling provides a wide operation range for the self-pulsation. Also, self-pulsating AFLs based on a loss-coupled DFB laser are experimentally demonstrated to verify the self-pulsation characteristics and the capability for all-optical clock recovery.