Photonic integrated transceiver for the access network

To reduce fabrication costs of fibre-optic terminal modules for interactive services, an InGaAsP/InP chip fabrication process has been developed for monolithic integration of a strained-layer multiple quantum well laser, a monitor diode and a photoreceiver with a 1300/1530nm filter. Reception responsivity and output power of the chips are 0.1 AW^-1 at 1300nm wavelength and 4.5mW at 1530nm wavelength, respectively. At present, complete modules with fibre pigtail exhibit 0.7mW launch power, but 1.4 mW is expected with the latest chips.     

A tunable diode-laser spectrometer for the MIR region near 7.2 μm applying difference-frequency generation in AgGaSe2

2 and two diode lasers as pump sources are presented. A single-mode Fabry–Pérot-type tunable diode laser (TDL) and an external-cavity diode laser (ECL) were combined to generate radiation in the mid-infrared region near 7.2 μm. With a TDL at a wavelength of approximately 1290 nm and an ECL emitting between 1504 and 1589 nm it was possible to carry out spectroscopic experiments concerning SO₂ at five different phasematching points between 1350 and 1400 cm^-1 by fixing the wavelength of one pump laser and tuning the wavelength of the other. With an input power of 8 mW for the single-mode Fabry–Pérot-type diode laser and 6 mW for the external-cavity laser an output power of about 10 nW was generated. Using the tuning capabilities of the external-cavity laser a spectral region up to 5 cm^-1 could be covered within one scan. Measurements of SO₂ absorption lines at low pressure demonstrate the high-resolution features of the spectrometer. Moreover, these data provide new direct experimental phasematching data for the rarely investigated spectral region at 7.2 μm. Received: 27 October 1997/Revised version: 8 May 1998     

Dual‐wavelength monolithic Y‐branch distributed Bragg reflection diode laser at 671 nm suitable for shifted excitation Raman difference spectroscopy

A dual‐wavelength monolithic Y‐branch distributed Bragg reflection (DBR) diode laser at 671 nm is presented. The device is realized with deeply etched surface DBR gratings by one‐step epitaxy. A maximum optical output power of 110 mW is obtained in cw‐operation for each laser cavity. The emission wavelengths of the device are 670.5 nm and 671.0 nm with a spectral width of 13 pm (0.3 cm⁻¹) and a mean spectral distance of 0.46 nm (10.2 cm⁻¹) over the whole operating range. Together with a free running power stability of ± 1.1% this most compact diode laser is ideally suited as an excitation light source for portable shifted excitation Raman difference spectroscopy (SERDS).     

Thermal- and Spectral-Characteristics of High-Power Quasi-Continuous Wave 940-nm InGaAs Diode Laser Arrays

Experimental results of the thermal and spectral characteristics of a monolithic stack of high power quasicontinuous wave 940-nm InGaAs linear laser diode arrays have been evaluated. Thermal resistance as the most important thermal parameter characterizing a high-power laser diode package was obtained using the temperature rise measured directly by a thermo-camera. A new simple and convenient technique to measure a spectral transition of the emission from laser diode arrays is proposed. Spectral chirping due to the transient thermal power dissipated during the laser pulse was observed as a time-evolution of the spectral profile; it gave a comprehensible image of the chirping behavior. Comparing the temperature rise in the diode junction with the thermal simulation, it was determined that the thermal shift of central wavelength dλ/dT was 0.21 nm/°C. Detailed performances were identified for pumping a Yb³⁺ doped crystalline laser, and it was verified that the laser diode arrays were satisfactory to meet pumping source requirements for coupling to Yb³⁺ absorption linewidth.     

Tapered diode lasers and laser modules near 635nm with efficient fiber coupling for flying-spot display applications

Flying-spot displays require light sources in the red, green and blue with a high optical output power and nearly diffraction limited beams. In this paper we present experimental results of red-emitting, AlGaInP based, tapered diode lasers and their integration into diode laser modules. The laser modules emit a collimated, almost diffraction limited beam with an optical output power as high as 1W at a wavelength close to 635 nm. The tapered laser chips were designed with emphasis on achieving a good beam quality in vertical and lateral directions of a collimated beam. To test the suitability for flying-spot display applications, we performed fiber coupling experiments with a low mode number optical fiber with an etendue as low as 6 × 10^?6 mm² sr. A maximum transmission of 70% of the launched power behind the uncoated fiber as well as a usable power in excess of 580mW were measured.     

High-efficiency direct-pumped Nd:YLF laser operating at 1321 nm

We present a high-efficiency Nd: LiYF₄ (Nd:YLF) laser operating at 1321 nm pumped directly into the emitting level, ⁴F_3/2. The linear polarization of the pump diode laser was maintained by a short fiber. At the absorbed pump power of 7.3 W, as high as 3.6 W of continuous-wave output power at 1321 nm is achieved. The slope efficiency with respect to the absorbed pump power was 0.52. To the best of our knowledge, this is the first demonstration of such a laser system. Comparative results obtained for the pump with a diode laser at 806 nm, into the highly absorbing ⁴F_5/2 level, are given in order to prove the advantages of 880 nm wavelength pumping.     

A cw AgGaS2 difference frequency spectrometer with diode lasers as pump sources

2 and two diode lasers as pump sources and experiments with this setup are presented. In contrast to the majority of known applications of the difference frequency mixing with solid state or gas lasers, we apply two single mode diode lasers with emission wavelengths of 690 nm and 805 nm, respectively. By fixing the emission wavelength of one diode laser and tuning the wavelength of the second laser, by changing temperature or excitation current, we can cover typically 0.87 cm^-1 (FWHM) in good agreement with recently published data and theory. With an input power of 20 mW and 6 mW we achieved an output power in the nW-range. To demonstrate the capabilities of the spectrometer we scanned CO and OCS absorption lines near 2107 cm^-1. From these experiments we deduce an overall signal-to-noise ratio of 1000:1 and a spectral resolution better than 30 MHz. With such parameters a trace gas detection of CO at sub-ppm level will be possible. Received: 19 August 1996/Revised version: 5 November 1996     

Diode-pumped Nd:YCOB self-frequency-doubling blue laser at 468 nm

We report a continuous-wave (CW) self-frequency-doubling blue laser at 468 nm by a diodepumped Nd³⁺:YCa₄O(BO₃)₃ (Nd:YCOB) laser. With 14.3 W of diode pump power, a maximum output power of 211 mW in the blue spectral range at 468 nm has been achieved. The beam quality M² values were equal to 1.16 and 1.23 in X and Y directions, respectively. The output power stability over 30 min is better than 5%. To the best of our knowledge, this is the highest power laser at 468 nm generated by self-frequency doubling of a diode pumped Nd:YCOB laser.     

利用光谱滤波器实现自启动的全光纤超短脉冲掺Yb3+光纤激光器

讨论了利用光谱滤波器实现自启动的被动锁模掺Yb³⁺光纤环形激光器的锁模机理,并研制出全光纤结构超短脉冲掺Yb³⁺光纤环形激光器.使用980 nm二极管激光器作为抽运源,高掺杂浓度掺Yb³⁺光纤作为增益介质.在净群速度色散为正的环形腔中加入光谱滤波器,抑制Yb³⁺离子在1030 nm强发射峰的同时,通过对啁啾脉冲的光谱滤波实现脉冲压缩.光谱滤波器与光纤非线性偏振旋转效应相结合,实现了激光器在1053 nm可自启动、十分稳定的锁模运转.激光器锁模阈值功率300 mW,平均斜率效率18.3%,最大输出功率53.07 mW,对应最大输出脉冲能量3.2 nJ.锁模光脉冲中心波长1053.6 nm,3 dB带宽10.84 nm,重复频率16.45 MHz.锁模脉冲宽度为皮秒量级,经腔外光栅对压缩至188 fs. 关键词： 3+光纤激光器')" href="#">掺Yb³⁺光纤激光器 自启动锁模 全光纤     

多波长红外激光二极管峰值光谱热漂移研究

为了满足红外激光测试技术对多光谱集成光源在光谱范围和峰值精度等方面的要求,提出了一种高精度的多波长红外激光二极管,并设计了能够集成860 nm,905 nm和1064 nm(脉冲/单模)四种激光芯片的封装结构.建立了基于上述封装结构下中心热沉的温度场分布模型,并根据数学建模工具求解的中心热沉温度场数值分布规范了中心热沉的加工工艺.为了验证多波长激光二极管中心热沉对输出峰值光谱热漂移现象的抑制效果,制备了多波长激光二极管样机,并搭建了观察其峰值光谱热漂移现象的实验装置.实验结果显示,样机仅有两种芯片的峰值光谱发生了1—3 nm的微弱漂移,并未超出规定的峰值半宽.该现象证明了多波长激光二极管的输出光谱具备较高的精度和良好的稳定性.     

Active laser frequency stabilization using neutral praseodymium (Pr)

We present a new possibility for the active frequency stabilization of a laser using transitions in neutral praseodymium. Because of its five outer electrons, this element shows a high density of energy levels leading to an extremely line-rich excitation spectrum with more than 25?000 known spectral lines ranging from the UV to the infrared. We demonstrate the active frequency stabilization of a diode laser on several praseodymium lines between 1105 and 1123 nm. The excitation signals were recorded in a hollow cathode lamp and observed via laser-induced fluorescence. These signals are strong enough to lock the diode laser onto most of the lines by using standard laser locking techniques. In this way, the frequency drifts of the unlocked laser of more than 30 MHz/h were eliminated and the laser frequency stabilized to within 1.4(1) MHz for averaging times >0.2 s. Frequency quadrupling the stabilized diode laser can produce frequency-stable UV-light in the range from 276 to 281 nm. In particular, using a strong hyperfine component of the praseodymium excitation line E=16?502.616_7/2 cm $^{-1}\rightarrow E'=25\,442.742^{\mathrm{o}}_{9/2}$  cm^?1 at λ=1118.5397(4) nm makes it possible—after frequency quadruplication—to produce laser radiation at λ/4=279.6349(1) nm, which can be used to excite the D₂ line in Mg⁺.     

High repetition-rate wavelength tuning of an extended cavity diode laser for gas phase sensing

A method for rapid wavelength tuning of an extended cavity diode laser (ECDL) is presented providing for high resolution, narrow bandwidth output over limited spectral regions. The method permits tuning over isolated spectroscopic features at repetition rates of tens of kHz, greatly exceeding conventional ECDL tuning speeds. In this paper we present high repetition rate laser induced fluorescence (LIF) spectroscopy of the 5²P_1/2 to 6²S_1/2 transition in indium at 410 nm, to demonstrate the technique. The presented ECDL design is very easy to implement, cheap and robust, as it employs no moving parts and can be used over all wavelength regions where FP diode lasers are available. This extends the usefulness of standard FP diode lasers to high speed sensing applications. Advantages and disadvantages of the technique are discussed. PACS 42.55.Px; 42.60.Fc; 42.62.Fi; 32.50.+d     

Sum frequency generation at 309 nm using a violet and a near-IR DFB diode laser for detection of OH

We have used a violet diode laser at 404 nm and a distributed feedback diode laser at 1320 nm to produce 0.8 nW of radiation at 309 nm by sum frequency generation in beta-barium borate. The UV radiation was tuned mode-hop-free over 30 GHz and used to detect OH radicals produced in a microwave discharge. By chopping the UV light at 500 Hz, we observed a concentration of 2×10¹² cm^-3 with a signal to noise ratio of 30:1. Received: 16 November 2001 / Revised version: 23 January 2002 / Published online: 14 March 2002     

Enhancement of the far-field output power and the properties of the very-small-aperture lasers

We report on a VSAL structure fabricated by a 650 nm edge emitting laser diode with an Au-coated facet and an aperture size of 250 × 500 nm. The far field output power can maintain at 1 mW and the power density is 7.5 mW/μm². Some properties of the VSAL including the threshold current change, the red-shift of the spectral position, and the strong relative-intensity-noise are presented. The physical mechanisms responsible for these phenomena are also discussed, which may contribute to the understanding and application of the potential device for near-field optics.     

Differential Helmholtz resonant photoacoustic cell for spectroscopy and gas analysis with room-temperature diode lasers

The results of theoretical and experimental studies and the design of a multi-purpose differential Helmholtz resonant photoacoustic detector (DHRD) and its applications to high-resolution spectroscopy of molecular gases and gas analysis with a room-temperature diode laser in the near-IR region are summarized. The series of experiments and numerical analysis of the DHRD sensitivity were performed for both types (single-pass and multi-pass) of DHRDs within a wide pressure range 0.1–101 kPa, including the regime of a gas flowing through a DHRD cell. The hardware and electronic arrangement of DHRDs for diode laser spectrometers and gas analyzers providing a limiting absorption sensitivity better than 10^-7 Wm^-1 are described. The results of measurements of spectral line parameters of H₂O near 800 and 1390 nm and CH₄ near 1650 nm (intensities, line broadening and shifting by atomic and molecular gases) are presented and discussed. The problems and the ways of perfection of the methodology and accuracy of DHRD techniques with tunable diode lasers of near-IR and visible spectral ranges are discussed. Received: 1 April 2002 / Revised version: 20 June 2002 / Published online: 21 August 2002 RID="*" ID="*"Corresponding author. Fax: +7/382-225-8026, E-mail: kvan@asd.iao.ru     

Tunable frequency-controlled laser source in the near ultraviolet based on doubling of a semiconductor diode laser

Continuously tunable ultraviolet laser radiation at 397 nm was generated by doubling the output of a semiconductor diode laser. The fundamental radiation was provided by a 150 mW AlGaAs laser diode injected by a low-power AlGaAs laser diode which was frequency stabilized by optical feedback using a new scheme of a miniature external cavity. Second-harmonic generation was produced in a lithium-triborate crystal placed in a compact enhancement cavity. The fundamental radiation was used for sub-Doppler spectroscopy of the Ar I 4s ³ P ⁰ ₀–4p ¹ P ₁ transition at 795 nm; the second-harmonic radiation was used for spectroscopy of the Ca II 4² S _1/2–4² P _1/2 transition at 397 nm.     

Diode laser spectrometer at 493 nm for single trapped Ba+ ions

+ ions. Frequency doubling of a 100 mW diode laser at 986 nm results in up to 60 mW output power at 493 nm in a bandwidth of less than 60 kHz with respect to the cavity used for locking. Reference frequencies of 18 spectral lines of Te₂ near the 493 nm resonance of Ba⁺ have been measured using modulation transfer spectroscopy. The fluorescence excitation spectrum of a single Ba⁺ ion, measured with this laser, exhibits well-resolved dark resonances, which confirms the versatility of the system for quantum optical experiments. Received: 12 June 1998     

Polarization‐resolved high‐resolution Raman spectroscopy with a light‐emitting diode

We demonstrate the use of a light‐emitting diode (LED) based experimental setup for collecting polarization‐resolved Raman spectra with good spectral resolution. The combination of a commercial red LED (630 nm), a 1‐nm bandwidth laser‐line filter, and a polarizing prism is used as a light source. Polarization‐resolved spectra in dimethyl sulfoxide are recorded and compared with the corresponding laser‐Raman spectra. The LED‐excited spectra exhibit a resolution slightly lower than those in the laser case but still close to the resolution of the spectrometer. All relevant spectral features of dimethyl sulfoxide including the symmetric and antisymmetric stretching modes of the CSC moiety are resolved with the experimental setup providing a spectral resolution of approximately 20 cm⁻¹. Copyright © 2013 John Wiley & Sons, Ltd.     

Diode-pumped continuous-wave Nd:YLF laser at 1313 nm

We present an efficiency Nd:LiYF₄ (Nd:YLF) laser operating at 1313 nm pumped directly into the emitting level ⁴ F _3/2. At the incident pump power of 10.3 W, as high as 3.1 W of continuous-wave output power at 1313 nm is achieved. The slope efficiency with respect to the incident pump power was 36.1%. To the best of our knowledge, this is the first demonstration of such a laser system. Comparative results obtained for the pump with diode laser at 806 nm, into the highly absorbing ⁴ F _5/2 level, are given in order to prove the advantages of the 880 nm wavelength pumping.     

Efficient Tm, Ho-co-doped silica fibre laser diode pumped at 1150 nm

High power and highly efficient operation of a Tm³⁺, Ho³⁺-doped silica fibre laser that is pumped with diode lasers operating at 1150 nm is demonstrated. Internal slope efficiencies approaching the Stokes limit were produced and the maximum output power was 2.9 W. High power diode lasers operating at 1150 nm are valuable pump sources for a range of fibre lasers offering output in the shortwave infrared spectrum.