A narrow-linewidth, low-noise hybrid integrated external cavity laser at 1550 nm is fabricated, the polarization maintaining fiber Bragg grating (FBG) as optical feedback component is coupled with the semiconductor gain chip, and the laser linewidth is reduced by the large group delay characteristics at the sloping side of the FBG reflectance spectrum. The butterfly-packaged laser realizes a single longitudinal mode and polarization-maintaining output of the single polarization laser, including the output power >= 30 mW with integral linewidth of 15.9 kHz at 1 kHz, the Lorentz linewidth of 4.85 kHz, the intrinsic linewidth of 4.06 kHz, the relative intensity noise <=-155 dB.Hz(-1) at 1 MHz, the polarization extinction ratio >25 dB, the current tuning range without mode hopping >= 8 GHz, the temperature tuning range without mode hopping >= 14 GHz, the power stability of 1.7% within 6 h, and the frequency variations <50 MHz.

The external cavity diode laser (ECDL) uses the LD chip as gain element and external reflectors as cavity mirrors, instead of the cleaved facets of LD chip. The cavity length can then be extended for a longer photon lifetime; and the external reflector may have strong wavelength selectivity to suppress mode competition effectively. The external reflector can provide an additional tuning method. In this Chapter, general characteristics and theory of ECDL are explained in Sect. 3.1 . ECDLs incorporated with planar diffractive gratings are described in Sect. 3.2 , especially the structures of Littrow type and Littman type. Section 3.3 introduces ECDL with Bragg gratings, including the fiber Bragg gratings (FBG), the waveguide Bragg grating (WBG) and the volume Bragg grating (VBG). Section 3.4 focuses on ECDL with external Fabry-Perot resonator and ring resonator.

The ordinary LD with an F-P cavity composed of cleaved facets works often in multiple longitudinal modes; and the mode frequency is susceptible to pump levels and environmental conditions. To make it working in a single longitudinal mode, especially in case of high frequency modulations, it is necessary to insert a wavelength selective element in the cavity. Three monolithically integrated Monolithically integrated laser semiconductor lasers with excellent characteristics of single longitudinal mode operation are introduced in this Chapter: the distributed feedback (DFB) laserDistributed Feedback (DFB) laser , the distributed Bragg reflector (DBR) laser, and the vertical cavity surface emitting laser (VCSEL) in three sections, respectively. All of them are based on the principle of Bragg refraction, but have different characteristics.

Stability of laser frequency is one of the most important performances. The frequency stabilization involves basically three parts: a reference frequency, i.e., the target frequency the laser frequency is to be locked, a frequency discriminator, and a method of feedback to tune the laser. The absorption lines of atoms or molecules are mostly often used references, especially for applications of laser spectroscopy. The saturated absorption spectroscopy with Doppler broadening removed is an important step in spectroscopy and in laser’s frequency stabilization, which is introduced in Sect. 6.1. The wavelength modulation and the frequency modulation spectroscopic methods of the frequency stabilization are discussed in Sect. 6.2. Schemes with modulation-free are developed, as described in Sect. 6.3. Section 6.4 is engaged in explanation of Pound–Drever–Hall (PDH) method, which uses the resonant peaks of high precision Fabry–Perot cavity as reference frequencies. The last section introduces schemes of self-mixing interference, one of the methods of active noise reduction.

A butterfly-packaged narrow-linewidth hybrid integrated external cavity diode laser module based on the polarization maintaining fiber Bragg grating is reported. The module emits at the wavelength of 1550 nm and provides 21 GHz of continuous tunability. It produces ≥ 20 mW of polarization maintaining fiber-coupled output power with intrinsic Lorentz linewidth ≤ 3 kHz and RIN ≤140 dB/√Hz@100 kHz. To qualify the reliability of the laser module under harsh environmental conditions, random vibration test and high-low temperature cycling test are carried out, and no degradation of the power current characteristic is observed.

Multiple trauma can induce sepsis and organ failure, even threaten people’s lives. To further study the mechanisms of multiple trauma, we analyzed microarray of GSE5760. GSE5760 was downloaded from the Gene Expression Omnibus including a total of 58 peripheral blood transcriptome from patients without (WT, n = 30) and carrying (MUT, n = 28) the tumor necrosis factor (TNF) rs1800629 A variant. The differentially expressed genes (DEGs) were screened using the limma package in R and the Benjamin and Hochberg method in a multi-test package. Then, functional enrichment analysis of DEGs was performed. Also, transcription factors significantly related to DEGs were searched using WebGestalt and interaction network of transcription factors and DEGs were constructed using STRING online software. Furthermore, pathway enrichment analysis for the DEGs in the interaction network was conducted using KO-Based Annotation System (KOBAS). We screened 39 DEGs including 27 upregulated and 12 downregulated genes. The enriched functions were associated with biological process (BP) (such as response to hypoxia, P value = 0.039803), cell components (CC) (such as mitochondrial part, P value = 0.043857), and molecular function (MF) (such as structural constituent of ribosome, P value = 0.008735). Besides, RPS7 and RPL17 were associated with ribosome and participated in ribosome pathway. PPP2R2B was related to mitochondrion. KCNMA1 , ALAS2 and SOCS3 were associated with hypoxia. Moreover, transcription factors of LEF1 , CHX10 , ELK1 , SP1 , and MAZ were significantly related to DEGs. RPS7 , RPL17 , PPP2R2B , KCNMA1 , ALAS2 , and SOCS3 might relate to multiple trauma. And TNF-α mutation could cause sepsis in patients with multiple trauma by changing the expression of these genes.

Quantum communication is a new technology requiring a stable and reliable laser source for communication security.A new kind of polarization-locked vertical-cavity surface-emitting laser (VCSEL) with polarization maintaining (PM) fiber pigtail is fabricated as a decoy state laser source.The VCSEL is packaged in a standard butterfly box integrated with thermoelectric coder (TEC) and thermistor.The optical pulse width of full-width at half-maximum (FWHM) is smaller than 400 ps with a 100-MHz on/off modulation frequency.The results reveal that modulation range is better than 4.Moreover, the polarization is stable, and the power extinction ratio is larger than 25.The center wavelength is 850 nm, and the SMSR is better than 40 dB.

The wavelength lateral distribution of high-power laser diode arrays (LDA) is tested. A V-type wavelength distribution is measured typically in the tested LDA. The measurements are carried under different driving currents, indicating that the thermal induced wavelength distribution is in protuberant shape and is opposite to the V-type. Based on the relation between stress and band-gap energy, it is show that the V-type stress distribution in LDA indicates the stress distribution in the laser chip. A linear stress distribution model is proposed to explain the experimental results. This work demonstrates that the measurement of lateral wavelength distribution can provide a useful method to detect bonding stress.

半导体激光器阵列的输出光功率密度较低、输出光束质量较差的缺点限制了它的广泛应用.介绍了提高输出光功率密度和输出光束质量的非相干技术--波长合成技术、偏振合成技术和空间交叉合成技术的最新进展,对实现各种技术的结构和实验结果进行了综述报道.

根据目前多数高功率半导体激光器模块只适合工作在准连续(QCW)状态下的特点,提出了利用光谱方法测量半导体激光器温升进而计算得到热阻的计算方法.该方法具有简单、直观、快捷的特点,同时避开了常规计算热阻方法要求半导体激光器工作在连续状态的局限性.其中在不同占空比、同一工作电流下得到的热阻值一致性较好,更接近文献给出的数值,具有实际应用价值.

半导体激光器阵列（LDA）封装过程中引入的应力是影响器件阈值电流、光束特性和寿命的重要因素,需要一种简单有效的测试半导体激光器阵列应力的方法评估检测器件封装的质量。分析了应力改变电荧光偏振度（DOP）的一系列理论机制,并通过对条形激光器阵列在荧光条件下偏振特性的测量,研究了几种不同封装形式的条形激光器阵列的荧光偏振度随外加应力的变化性质。实验表明,半导体激光器阵列的偏振特性随驱动电流的增加变化明显,尤其是在阈值电流附近,偏振特性急剧变化。当有局部外力作用器件时,器件的荧光偏振度分布明显变化。通过对多个不同材料封装器件的荧光偏振度测试比较,发现不同的材料和封装形式对管芯引入的封装应力有明显的差别。

太阳能被认为是人类在21世纪将取代传统化石能源的最佳选择之一,它是一种可以再生的绿色能源。基于近年来所阅读的文献资料,较为系统地介绍了太阳能发电技术（PV）发展的状况,包括太阳能电池及相关的光学技术;并简单介绍世界和我国太阳能产业发展状况和趋势。从国际上的技术进展看,今后10余年将是太阳能发电技术和产业大发展的时期。预计2020年前后,太阳能发电将在经济上胜过传统技术而成为电网的主力;在技术上,基于Ⅲ-Ⅴ族化合物半导体的多重结高效率太阳能电池,配合大聚焦比光学系统的聚焦型太阳能发电（CPV）,是最有发展前途的方向之一。

High-power laser diodes(HPLD) spectral linewidth is relatively broad(approximately 2～4 nm).The wavelength shifts with temperature(by approximately 0.3 nm/K) and changes with current,and the beam quality is poor.Therefore,research on the thermal characteristics and wavelength stabilization of HPLD becomes one of the most important topics in the field.An external cavity laser was built using Volume Bragg Grating as feedback element and high power semiconductor linear array to lock it's stimulated wavelength.The relationship was analyzed among the wavelength locked and it's operational current,cooling temperature,duty cycle of the current and smile.The results indicate that the stimulated wavelength is influenced by the operational current,cooling temperature and the duty cycle.Besides the wavelength locked is better when the wavelength difference between the free running and the VBG Bragg wavelength is smaller than 3.0 nm,while wavelength locked wasn't influenced by it's smile.