Numerical study of converting beat-note signals of dual-frequency lasers to optical frequency combs by optical injection locking of semiconductor lasers

The optical injection locking of semiconductor lasers to dual-frequency lasers is studied by numerical simulations. The beat-note signals can be effectively transformed to optical frequency combs due to the effective four wave-mixing in the active semiconductor gain medium. The low-noise Gaussian-like pulse can be obtained by locking the relaxation oscillation and compensating the gain asymmetry. The simulations suggest that pulse trains of width below 30 ps and repetition rate in GHz frequency can be generated simply by the optical injection locking of semiconductor lasers. Since the optical injection locking can broaden the spectrum and amplify the optical power simultaneously, it can be a good initial stage for generating optical frequency combs from dual-frequency lasers by multi-stage of spectral broadening in nonlinear waveguides.     

Synchronization of chaotic erbium-doped fibre lasers and its application in secure communication

We have investigated the synchronization of chaotic dual-ring erbium-doped fibre lasers using the delay feedback－injection scheme. Numerical simulation shows that two chaotic dual-ring erbium-doped fibre lasers can be well synchronized if the strengths of delay feedback and injection are suitable. Even though the effects of the noises and the difference between the two lasers are considered, the twins can still reach good synchronization. Secure communication could be realized using the scheme of message-masking based on the synchronization of the chaotic dual-ring erbium-doped fibre lasers.     

Synchronization of Chaotic Intensities and Phases in an Array of N Lasers

A linear array of N mutually coupled single-mode lasers is investigated. It is shown that the intensities of N lasers are chaotically synchronized when the coupling between lasers is relatively strong. The chaotic synchronization of intensities depends on the location of the lasers in the array. The chaotic synchronization appears between two outmost lasers, the second two outmost lasers, etc. There is no synchronization between nearest neighbors of the lasers. If the number of N is odd, the middle laser is never synchronized between any lasers. The chaotic synchronization of phases between nearest lasers in the array is examined by using the analytic signal and the Gaussian filter methods based on the peak of the power spectrum of the intensity. It can be seen that the message of chaotic intensity synchronization is conveyed through the phase synchronization.     

Communications using multi—mode laser system based on chaotic synchronization

The communication using chaotic synchronization between two multi-mode Nd:YAG lasers has been investigated numerically.The digital communication using multi-mode chatoic lasers is quite different from that using single mode lasers.By introducing a short break between two adjacent bits in the communication shceme,the digital signals can besuccessfully encoded into the spiky pulses and decoded through the subtraction of receiver output from the transmitted.Even when the two multi-mode lasers are not synchronized perfectly with certain deviations,the encoded digits can still be decoded correctly.     

Mode locked and distributed feedback silicon evanescent lasers

Electrically pumped lasers that can be made on silicon and integrated with other components are important in order to take full advantage of the capabilities of silicon photonics. In this paper we review two specific types of hybrid silicon evanescent lasers that can fulfill these requirements. We discuss recent results of distributed feedback (DFB) lasers and mode locked lasers made on silicon using evanescent coupling to thin films of III‐V material. Device designs and test results are discussed in detail.     

Generation of ultrasound in materials using continuous-wave lasers

Generating and detecting ultrasound is a standard method of nondestructive evaluation of materials. Pulsed lasers are used to generate ultrasound remotely in situations that prohibit the use of contact transducers. The scanning rate is limited by the repetition rates of the pulsed lasers, ranging between 10 and 100 Hz for lasers with sufficient pulse widths and energies. Alternately, a high-power continuous-wave laser can be scanned across the surface, creating an ultrasonic wavefront. Since generation is continuous, the scanning rate can be as much as 4 orders of magnitude higher than with pulsed lasers. This paper introduces the concept, comparing the theoretical scanning speed with generation by pulsed laser.     

Self-mixing interference effect of DFB semiconductor lasers

This paper analyzes the self-mixing interference in DFB (distributed feedback) semiconductor lasers. The general expression of the threshold gain and frequency in the DFB lasers was deduced. Numerical simulations indicate that, for specific coupling coefficient and cavity length value, the DFB lasers are more sensitive to optical feedback than the Fabry–Perot semiconductor laser. These results show that high-accuracy self-mixing sensors can be obtained by using the DFB lasers. PACS 42.55.Px; 42.60.Lh; 42.87.Bg     

Synchronization and coherent combining of two pulsed fiber lasers

We demonstrate a scalable architecture for coherent combining of pulsed fiber lasers.A new method for generating synchronous pulsed fiber lasers by direct phase modulation is proposed and investigated.It is shown that phase modulated mutually coupled laser array can be a steady synchronous pulsed fiber laser source.The synchronous pulsed fiber lasers are coherently combined with an invariable phase difference of π in adjacent lasers.Neither active phase control nor polarization control is taken in our experiment.     

Synchronous implementation of optoelectronic NOR and XNOR logic gates using parallel synchronization of three chaotic lasers

The parallel synchronization of three chaotic lasers is used to emulate optoelectronic logic NOR and XNOR gates via modulating the light and the current. We deduce a logical computational equation that governs the chaotic synchronization, logical input, and logical output. We construct fundamental gates based on the three chaotic lasers and define the computational principle depending on the parallel synchronization. The logic gate can be implemented by appropriately synchronizing two chaotic lasers. The system shows practicability and flexibility because it can emulate synchronously an XNOR gate, two NOR gates, and so on. The synchronization can still be deteceted when mismatches exist with a certain range.     

飞秒激光与细胞的相互作用

近年来,高速发展的激光技术已经广泛应用于医疗领域,比如眼科手术和光学相干层析成像。尤为特殊的是,飞秒激光更可专用于对活体细胞的基础研究。飞秒激光具有别种激光无法获得的特殊性质。它对于细胞的伤害很小,因为它的线性吸收和热效应远远低于连续光。此外,由于飞秒光的超高峰值功率,它可以对细胞形成多光子电离而在细胞膜上开孔,因此可以转基因和融合细胞,同时不会太过于伤害细胞。在这个报告里,将阐述我们的以下研究：飞秒光致转基因、细胞融合以及细胞在凋亡中的动态过程。在单细胞水平上提出了一些凋亡过程的可能机制,如活性氧化合物、核管和细胞内自由钙离子的产生。     

Limits of Coherent Addition of Lasers: Simple Estimate

The coherent combining of single mode lasers using coupled cavities is considered. A simple analytical estimate of the number of lasers that can be efficiently combined in such a way is suggested. Such an estimate agrees with simulations and experiments reported recently.     

Synchronization and coherent addition of three pulsed fiber lasers by mutual injection and phase modulation

The coherent beam addition of pulsed fiber lasers is an effective way to improve the average power and the peak pulse power. We demonstrate a new architecture based on mutual injection and phase modulation to generate synchronous pulsed fiber lasers. Firstly, we realize the synchronization of the pulses of three fiber lasers using this technique. Secondly, coherent addition of three synchronous pulsed fiber lasers is obtained. Experimental results show that the three fiber lasers are phase locked and have good temporal and spatial coherence under mutual injection locking. This method can be extended to combine more beams.     

Control of peaks of terahertz radiation and tuning of its frequency and intensity

We propose to employ dark hollow laser beams (DHBs) for obtaining multifocal terahertz (THz) radiations which are quite useful in medical applications. The number of peaks in the THz field can be suppressed if we apply external magnetic field and use intense lasers so that the relativistic effects are prominent. It means we can achieve strong bifocal THz radiation with this scheme. However, multifocal THz radiation can be reconstituted by increasing the beating frequency of the lasers. The separation of the peaks can be controlled by wisely choosing the orders of the lasers, and also by varying the strength of the magnetic field. The magnetic field is found to enhance the THz field, and also it tunes the frequency of the THz field. The DHBs of higher and equal orders are found to be most significant for efficient THz radiation generation with respect to the role of the magnetic field and density ripples.     

Simultaneous bidirectional message transmission in a chaos-based communication scheme

We introduce a chaos-based communication scheme allowing for bidirectional exchange of information. Coupling [corrected] two semiconductor lasers through a partially transparent optical mirror, placed in the pathway connecting the lasers [corrected] delay dynamics is induced in both lasers. We numerically demonstrate that this dynamics can be identically synchronized, and moreover, information introduced on both ends of the link can be simultaneously transmitted. This scheme allows one to negotiate a key through a public channel.     

单量子点微腔激光器的研究

研究一个三能级量子点耦合到单模光学腔组成的系统,该单量子点激光器的泵浦阈值较小,激光能较快地达到稳定输出,当量子点和腔模耦合强度增强时,其泵浦阈值更小,激光达到稳定输出的速度更快。     

Collimation tester for ultrashort pulses and short coherence length lasers

A simple and easy-to-use collimation tester suitable for short coherence length lasers is described. The device is based on shearing interferometry using a compensation plate that enables a zero path length difference of the interfering beams and can be used for lasers of virtually vanishing coherence length, such as found in fs-lasers and high-power multimode lasers.     

An acousto-optical deflection system for use with multi-laser arrays in optical memories

Proposals have been made to utilise arrays of GaAs lasers in optical computer memories. For fast, random access to data the use of acousto-optical deflectors seems feasible. The number of lasers for use with each deflector is normally severely limited, because of the bandwidth limitation which is inherent in acousto-optic devices. This note describes a technique whereby the bandwidth limitation can be largely overcome, so that light from many lasers can be deflected by a single deflector.     

Realization of Optical Phase Locked Loop at 9.2GHz between Two Independent Diode Lasers

The optical-phase-locked-loop (OPLL) at 9.2GHz between two independent narrow linewidth diode lasers is realized. Ultrabroad servo bandwidth at 4MHz is first achieved and it is guaranteed that the full spectral characteristics of the master laser can be transferred to the slave laser. The experimental results prove that the coherence between two lasers is about 99%. This offers a new method to study the interaction between lasers and atoms based on the ground hyperfine structure of caesium atoms.     

表面等离子体激元纳米激光器技术及应用研究进展

传统半导体激光器由于采用光学系统反馈而存在衍射极限,其腔长至少是其发射波长的一半,因此难以实现微小化。基于表面等离子体激元的纳米激光器可以实现深亚波长乃至纳米尺度的激光发射,而且现代微纳加工技术的逐步成熟,也为亚波长乃至纳米量级激光器的研制提供了成熟的技术条件。本文重点综述了国际上已成功实验验证的基于表面等离子体激元的纳米激光器的最新研究进展,综述了表面等离子体激元的基本原理,给出了若干种表面等离子体激元纳米激光器的结构和特点,指出该类激光器现存问题主要表现在激元损耗高及由此引起的制备工艺和电泵浦涉及的技术难题。文中最后展望了纳米激光器的应用和研究前景。     

散射颗粒分布对二维随机激光器腔内各模式的影响

采用时域有限差分法数值求解Maxwell方程组,分析了二维随机激光器中光波模式的频谱特性.计算表明,处于不同分布区域的散射颗粒对腔内不同模式的影响有很大差异,处于该模式空间分布区域的散射颗粒比区域外的颗粒对模式有更大的影响.这个特性是随机激光器所独有,并可以用来进行随机激光器的模式选择.