Quantum-dot semiconductor optical amplifier performance management under optical injection

The effect of an external beam on different characteristics of quantum-dot semiconductor optical amplifiers (QD-SOAs) has been investigated experimentally. It has been shown that injection of a relatively weak light beam at the gain transparency wavelength accelerates the full gain recovery time from 80 ps to 65 ps while it increases the saturation output power (SOP) by more than 2 dB if the beam resides in the gain region. The effect of the external beam on the fiber-to-fiber gain has been demonstrated at both the gain transparency wavelength and close to gain peak wavelength. These results are expected to be further enhanced by increasing the injected beam power, which has a peak value of ～7 mW in the experiments.     

Narrow-linewidth master-oscillator power amplifier based on a semiconductor tapered amplifier

The output of a grating-stabilized external-cavity diode laser was injected into a semiconductor tapered amplifier in a master-oscillator power amplifier configuration, producing as much as 500 mW of power with narrow linewidth. The additional linewidth that is due to the tapered amplifier is much smaller than the typical linewidth of grating-stabilized laser diodes. To demonstrate the usefulness of the narrow linewidth and high output power, we used the system to perform Doppler-free two-photon spectroscopy with rubidium.     

Saturated semiconductor optical amplifier phase modulation for long range laser radar applications

We investigate the use of a semiconductor optical amplifier operated in the saturation regime as a phase modulator for long range laser radar applications. The nature of the phase and amplitude modulation resulting from a high peak power Gaussian pulse, and the impact this has on the ideal pulse response of a laser radar system, is explored. We also present results of a proof-of-concept laboratory demonstration using phase-modulated pulses to interrogate a stationary target.     

Comparative analysis of triple band S-C-L erbium-doped fibre and semiconductor optical amplifier for CWDM applications

The authors present a comparative analysis between a triple-band S-C-L erbium-doped fibre amplifier and a commercial semiconductor optical amplifier in a CWDM application scenario. Both technologies were characterised for gain and noise figures from 1480 to 1610 nm (S, C and L bands) and their systemic performances were evaluated in terms of bit error rate measurements for a wide range of optical power levels.     

Suppression of self-pulsing behavior in erbium-doped fiber lasers with a semiconductor optical amplifier

We experimentally demonstrate that the stability of cw and mode-locked erbium-doped fiber ring lasers can be improved significantly with a semiconductor optical amplifier (SOA) inside the cavity. The fast saturable gain of the SOA suppresses significantly the self-pulsing that is due to ion pairs in the erbium-doped fiber, which acts as a saturable absorber. A linear stabilization analysis of the laser system agrees with our experimental results.     

通信用聚合物光纤放大器

通过对掺杂有机燃料聚合物光纤放大器、掺杂稀土螯合物聚合物光纤放大器、聚合物光纤拉曼放大器以及半导体聚合物光纤放大器的基本原理和特点以及近期新发展的介绍,指出了几种聚合物光纤放大器的研究方向.     

Polarisation effects on the nonlinear optical characteristics of a 1.55 μm vertical-cavity semiconductor optical amplifier

The effect of polarisation on the nonlinear optical properties of a 1550 nm vertical- cavity semiconductor optical amplifier (VCSOA) subjected to external optical injection into the two orthogonal polarisations of the fundamental mode has been studied experimentally. Clockwise nonlinear switching with very high on-off contrast ratio between the output states, exceeding 50:1, is reported. It is also shown that the use of polarised light gives a reduction to only some tens of microwatts of the input power requirements needed for clockwise nonlinear switching with high on-off contrast ratio. This represents at least one order of magnitude decrease in comparison with previously reported results either in VCSOAs or in edge-emitting devices. These results offer promise for the potential use of VCSOAs for all-optical signal processing as well as for optical interconnects and all-optical switching/routing applications.     

512-channel vertical-cavity surface-emitting laser based free-space optical link

A vertical-cavity surface-emitting laser based bidirectional free-space optical interconnect has been implemented to interconnect two printed circuit boards. A total of 512 clustered channels with a density of 2844 channels/cm2 are transmitted over a distance of 83 mm. The optical interconnect is a combination of refractive microlenses and diffractive minilens relays.     

Fiber-optic temperature sensor used for oil well based on semiconductor optical absorption

This paper describes an optical-fiber sensor developed for temperature measurement under offshore oil well conditions. The sensor exploits the displacement of the optical absorption edge occurring in semiconductors under the influence of temperature variation as a result of temperature-induced energy shifting of conduction band extrema. The structure of the sensor and the measurement principle are described. The common-path reference measurement and node type error compensation technologies are developed. And, the detailed theoretical analysis indicates that the proposed sensor system can effectively improve measurement errors caused by light fluctuation, difference and variation of the detector responsiveness, circuit magnification times, and so on. It proves that this sensor system can be applied under long-term formidable conditions with fairly good measurement stability.     

High-throughput optical processors based on semiconductor nanostructures for incoherent-light optical analog computers with parallel image processing

Fast-response optical recording media based on semiconductor nanostructures (CdTe, GaAs) have been developed for image recording and processing at a speed of up to 10⁶ cps, which is 2–3 orders of magnitude higher than the speed of well-known media based on liquid crystals (MIS-LC). The new media are characterized by a photosensitivity of 10^?2 W/cm² and a spatial resolution of 5–10 lines/mm. Methods for the readout of images recorded in the nanostructures are developed and high-speed incoherent-light optical processors based on these structures are created. The possibility of using these processors for building optical analog computers and image correlators is demonstrated.     

MOEMS阵列光开关的微反射镜的制作

通过各向异性湿法腐蚀工艺利用 (110 )硅片制作了 8× 8阵列光开关的微反射镜阵列 ,反射镜面为 { 111}面 ,表面粗糙度低于 10nm ,垂直度好于用同样的方法在 (10 0 )硅片上制作的反射镜。     

Spectral characteristics of a regenerative semiconductor optical amplifier mutually injection locked with a Fabry-Perot laser diode

The anomalous injection locking of a traveling-wave semiconductor optical amplifier (SOA) and a fiber-pigtailed Fabry-Perot laser diode (FPLD) linked with single-mode and improved side-mode suppression ratio output is demonstrated. We achieve this injection locking by driving the FPLD slightly below threshold and by feedback injecting the FPLD with fractional output of a closed-loop SOA. The SOA-FPLD link lases in a single FPLD longitudinal mode with a reduced linewidth of 0.013 nm and a maximum side-mode-suppressing ratio of 39.7 dB. A precise 3-dB linewidth of 45-50 MHz is also observed from the self-homodyne mode-beating spectrum. The optimized feedback-injecting power for the FPLD is approximately 2% of the SOA-FPLD linked output power of >400 microW. The variations in output power and in peak wavelength are not more than 0.54% and 0.06%, respectively. The injection-locked SOA-FPLD link is insensitive to the temperature fluctuation within +/- 0.25 degrees C.     

基于电吸收调制器的40Gbit/s光发射单元

采用电吸收调制器(EAM)作为电光调制器件,实现了基于电时分复用(ETDM)工作方式的40Gbit/s光发射单元,并采用SDH 42.836(Gbit/s标准数据库)对其进行了测试实验.在42.836Gbit/s数据率下,其输出光信号消光比达10dB以上,光眼图信噪比约11.4,抖动方均根值1.3～1.4ps;在G.652光纤中传输1km后,消光比大于9dB,光眼图信噪比约7.1,抖动方均根值为1.4～1.5ps,这些技术指标达到了实用要求.     

Single-mode near-infrared optical parametric oscillator amplifier based on periodically poled KTiOPO4

A singly resonant, single-axial-mode, optical parametric oscillator (OPO) based on periodically poled KTiOPO(4) (PPKTP) is reported. Signal (1.68 mum) and idler (2.90 mum) optical bandwidths have been narrowed to <400 MHz by use of a diffraction grating at grazing incidence. The OPO generates 370 muJ of signal radiation when pumped by 3.1 mJ of 1.064-mum radiation. We implemented a single-pass PPKTP amplifier to yield 2.15-mJ signal and 1.17-mJ idler radiation without broadening the spectral bandwidths.     

Misalignment correction for optical interconnects using vertical cavity semiconductor optical amplifiers

In board-to-board optical interconnects, the misalignment between the board and the backplane connections can cause both optical loss and interchannel cross talk. A vertical cavity semiconductor optical amplifier (VCSOA) is proposed to correct optical misalignment in an optical connector between the board and the backplane. Angular or lateral misalignment can be corrected with the designed module. The correction ability is determined by the acceptance angle of the VCSOA, which was characterized to be 9.4 degrees full angle at a 3 dB gain drop for a 30 microW optical signal at 1 GHz. The lateral misalignment correction ability is 0.16f, where f is the focal length of the mini lens to converge the input light onto the VCSOA.     

Improved design of a polarization converter based on semiconductor optical waveguide bends

By using an efficient vector finite-element-based beam-propagation method, we present an improved design of a polarization converter. This design relies on the use of a single-section deeply etched bent semiconductor waveguide with slanted sidewalls. By careful adjustment of the bend radius, the waveguide width, and the sidewall angle we obtained a nearly 100% polarization conversion ratio with no appreciable radiation loss and a bending angle of less than 180 degrees .     

Adaptive optical transmitter and receiver for space communication through thin clouds

Optical space communication from satellite to ground or air to air consists of clouds as part of communication channels. Propagation of optical pulses through clouds causes widening and deformation in the time domain and attenuation of the pulse radiant power. These effects decrease the received signal and limit the information bandwidth of the communication system. Having dealt with the other effects previously, here we concentrate on pulse broadening in the time domain. We derive a mathematical model of an adaptive optical communication system with a multiscattering channel (atmospheric cloud). We use knowledge about the impulse response function of the cloud to adapt the communication parameters to the transfer function of the cloud. The communication system includes a receiver and a transmitter. We adapted the transmitter to atmospheric conditions by changing the bit error rate. One can adapt the receiver to the atmospheric condition by changing the parameters of the detector and the filter. An example for a practical communication system between a low Earth orbit satellite and a ground station cover by cloud is given. Comparison and analysis of an adaptive and semiadaptive system with cloud channels are presented. Our conclusion is that in some cases only by such adaptive methods is optical communication possible.     

Multiple transmitter performance with appropriate amplitude modulation for free-space optical communication

The propagation of a free-space optical communications signal through atmospheric turbulence experiences random fluctuations in intensity, including signal fades, which negatively impact the performance of the communications link. The gamma-gamma probability density function is commonly used to model the scintillation of a single beam. One proposed method to reduce the occurrence of scintillation-induced fades at the receiver plane involves the use of multiple beams propagating through independent paths, resulting in a sum of independent gamma-gamma random variables. Recently an analytical model for the probability distribution of irradiance from the sum of multiple independent beams was developed. Because truly independent beams are practically impossible to create, we present here a more general but approximate model for the distribution of beams traveling through partially correlated paths. This model compares favorably with wave-optics simulations and highlights the reduced scintillation as the number of transmitted beams is increased. Additionally, a pulse-position modulation scheme is used to reduce the impact of signal fades when they occur. Analytical and simulated results showed significantly improved performance when compared to fixed threshold on/off keying.     

Integrated semiconductor optical sensors for cellular and neural imaging

We review integrated optical sensors for functional brain imaging, localized index-of-refraction sensing as part of a lab-on-a-chip, and in vivo continuous monitoring of tumor and cancer stem cells. We present semiconductor-based sensors and imaging systems for these applications. Measured intrinsic optical signals and tissue optics simulations indicate the need for high dynamic range and low dark-current neural sensors. Simulated and measured reflectance spectra from our guided resonance filter demonstrate the capability for index-of-refraction sensing on cellular scales, compatible with integrated biosensors. Finally, we characterized a thermally evaporated emission filter that can be used to improve sensitivity for in vivo fluorescence sensing.