Room-temperature optically-pumped GaSb quantum well based VCSEL monolithically grown on Si (100) substrate

Monolithic vertical cavity surface emitting lasers (VCSELs) on Si are demonstrated. The GaSb multi-quantum well active region embedded in an Al(Ga)Sb half-wave cavity spacer layer enables lasing under room-temperature optically-pumped conditions. The 13% lattice mismatch is accommodated by a spontaneously formed 2-D array of 90/spl deg/ misfit dislocations at the AlSb/Si interface. This growth mode produces very low defect density (/spl sim/8/spl times/10/sup 5//cm/sup 2/) and relaxed materials growth (98%) without the use of a buffer layer. Presented are VCSEL lasing spectra, light-in against light-out curves along with defect density measurements performed by microscopy and etch-pit density. A threshold excitation density of I/sub th/=0.1 mJ/cm/sup 2/ and a multimode lasing spectrum peaked at 1.62 /spl mu/m, results from a 3 mm pump-spot size.     

切换式双波长激发在掺镱和铒镱共掺复合式光纤激光器中的实现

抽运旁通腔型的掺镱光纤(YDF)激光器内剩余的抽运光功率随着入射抽运功率的变化呈现出光学双稳特性,这导致了用它来抽运另一个分叉腔的铒镱共掺光纤(EYDF)增益介质可获得第二个信号波长激发的可能性。根据这一原理,从实验上获得了1040 nm和1537 nm两个激发线的可切换振荡,这表明基于掺镱光纤激光器光学双稳态的复合腔结构(掺镱光纤激光器的抽运旁通腔和铒镱共掺光纤分叉腔)是实现切换式双波长光纤激光器光源的一个简单有效的方法。     

Photoluminescence excitation spectroscopy of the dense exciton gasinvolved in the lasing transition in ZnSe epitaxial layers

The lasing transition in ZnSe epitaxial layers has been investigated at 77 K. The lowest lasing threshold (I_th) was achieved when the layers were resonantly excited at the photon energy of the exciton level. It was found that the exciton level at the excitation intensity just above the I_th was red-shifted by about 16 meV compared with the free exciton line (2.792 eV) under weak excitation condition. The energy difference between the exciton line and the lasing peak was about 19 meV at I=I_th and increased with increasing excitation intensity up to I=8×I_th. This suggests that the stimulated emission occurs due to the inelastic exciton-exciton scattering process at this temperature     

Exciton Dynamics and Optically Pumped Lasing in 1-Naphthylmethylamine-Based Quasi-2D Perovskite Films

Films of the quasi-2D perovskite based on 1-naphthylmethylamine (NMA) are promising as the gain medium for optically pumped lasing and future electrically pumped lasing because of its low lasing threshold and small electroluminescence efficiency rolloff. However, reasons for the low threshold and small efficiency rolloff are still unclear. Therefore, exciton dynamics are investigated in NMA-based quasi-2D perovskite films. It is found that quenching of bright excitons by other excitons or charge carriers is unlikely in NMA-based quasi-2D perovskite films, which is one reason for the low lasing threshold and small efficiency rolloff. Moreover, thermally stimulated current measurements reveal that the defect levels inside the band gap of the NMA-based quasi-2D perovskite are shallow, with a depth of ≈0.3 eV, causing a decrease in nonradiative exciton recombination through the defects. Therefore, population inversion can be easily achieved, leading to the low lasing threshold as well. For fabrication of NMA-based quasi-2D perovskite laser devices with even lower lasing thresholds, a circular-shaped optical resonator, and small-molecule-based defect passivation are used. Optically pumped lasing can be obtained from these devices, with a threshold of ≈1 µJ cm⁻², which is one of the lowest values ever reported in any perovskite lasers.     

开放系统相位涨落对布居差和激光性质的影响

本文在考虑驱动场相位涨落时开放的简单三级系统的定态行为。结果表明，驱动场相位涨落将导致有限线宽。增益和被探测场耦合的两个能级间布居差将随线宽的增加而改变，并在有限线宽下发生从无粒子数反转激光到有粒子数反转激光的改变。     

Analysis of quenching conditions of Fabry-Perot mode lasing in semiconductor stripe-contact lasers

Radiative characteristics of semiconductor stripe-contact lasers operating under quenching conditions of Fabry-Perot-mode lasing are studied. It is found that reversible turning off of Fabry-Perot-mode lasing is caused by switching to closed-mode lasing. Radiative characteristics of the closed mode are controlled by the mode structure with the close-to-zero loss for radiation output, which covers the entire crystal. The main threshold conditions of closed-mode lasing are a decrease in interband absorption in the passive region and an increase in the modal gain of the closed-mode lasing line. It is shown that a decrease in interband absorption in the passive region can be provided by both spontaneous emission from the injection region and lasing-mode photons. An increase in the modal gain of the closed-mode lasing line is provided by shifting the energy minima of the conduction band and maxima of the valence band of the injection region with respect to the energy bands of the passive region.     

On the problem of lasing in traps for the bose condensation of dipolar excitons

Polariton-mode lasing in traps for the Bose condensation of dipolar excitons is considered and conditions under which this type of lasing takes place are examined. The width of the spectrum of the polariton modes involved in lasing and the role of the spatial and spectral inhomogeneity of the exciton distribution are discussed. The possibility of lasing in a system close to the exciton Bose condensation threshold is investigated in detail. The effect of inhomogeneous broadening of the exciton spectral line on the stability of steady-state lasing is analyzed. Experiments that help to reveal contributions from different physical processes to polariton-mode lasing in semiconductor structures designed for the Bose condensation of excitons are proposed.     

A new laser line in tin using stannic chloride vapor

A tin lasing line at 6579 Å has been observed in a pulsed gaseous discharge in SnCl4vapor. Lasing was also observed on Cl II lines in the discharge. The laser output had an annular appearance and the tin line lased only during the period of current increase.     

Fast Calculation of Cavity-Mode Characteristics of Photonic Crystal Cavities

A fast approach based on effective index perturbation method is proposed to evaluate the intrinsic characteristics of photonic-crystal-slab-based microcavity with two-dimensional finite-difference time-domain (2-D FDTD) technique. For two widely used single defect structures, less than 2% computational error was obtained in calculating the defect mode frequencies. Accurate prediction of cavity modal properties and resonant peak frequencies is feasible based on 2-D FDTD simulation by adjusting the effective index to match the dielectric band edge for donor-like defect mode. The correlation between the modified effective index and the cavity (lasing) mode with the highest quality factor$Q$offers an efficient tool in the design of defect mode based photonic crystal microcavities.     

Emission-line broadening of current tunable InAsSbP/InAsSb/InAsSbP heterostructure lasers

The dependence of emission-line broadening on the drive current was studied at 50–80 K for tunable InAsSbP/InAsSb/InAsSbP double heterostructure lasers operating in the 3.3–3.4 μm spectral region. For a small increase of the injection current I over the threshold current I _th, the line width depends on the I-I _th difference hyperbolically, in accordance with the Schawlow-Townes and Henry theories that assume a homogeneous distribution of the nonequilibrium carrier concentration across the resonator width. With the current raised to (3–4)I _th, line narrowing ceases and the line starts to broaden with increasing current. The observed line broadening is explained by the effect of the nonequilibrium carrier concentration gradient between the middle of the resonator and its edges. In tunable lasers, this gradient increases with current, the lasing wavelength simultaneously decreasing. The minimal width of the lasing line is 10–20 MHz. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 34, No. 12, 2000, pp. 1468–1471. Original Russian Text Copyright ? 2000 by Imenkov, Kolchanova, Kubat, Civish, Yakovlev.     

开放的梯型系统中相位涨落的影响

给出了有驱动场位相涨落的开放的梯型无粒子数反转激光（LWI）系统增益、色散和布居数差的定态解析解，进而用得到的数值计算结果分析了驱动场位相涨落对增益、色散和布居数差的影响。研究结果表明，驱动场位相涨落将导致有限线宽；随着线宽的增加，系统增益单调地减小，但系统色散的变化并不是单调的，当线宽取某个值时，色散有极大值；线宽的变化不能导致无反转激光向反转激光的转变。     

用于大气吸收测量的小型电激励连续波DF/HF选线化学激光器

介绍了用于大气吸收测量的电激励双模块小型连续波DF/HF选线化学激光器,描述了其结构、运转方式和激光器的性能。在采用一级振荡、一级输出的利特罗(Littrow)自准直光栅色散腔结构的前提下,激光器目前共获得17支DF激光谱线,11支HF激光谱线,大部分单谱线基横模输出超过1 W,单次连续出光时间超过30 min,功率稳定性在±5%以内。将激光器激光光栅改装为球面腔镜后也可输出多谱线DF/HF激光,功率水平为20 W,选模后基横模输出6~8 W。     

基于光纤拉锥及相位调制的可切换多波长掺铒光纤激光器

研究了一种全光纤可切换多波长掺铒光纤激光器。该激光器利用一段缠绕在压电陶瓷上的单模光纤作为正弦相位调制器以及基于光纤拉锥的马赫-曾德尔干涉仪作为梳状滤波器,抑制由于掺铒光纤的均匀展宽效应引起的模式竞争,从而避免了在室温下不稳定的单波长激射,实现了多波长掺铒光纤激光器的稳定输出。实验中观察到稳定的5个波长的同时激射,相邻波长间隔为0.804 nm。信噪比大于40 dB,3 dB带宽约为0.023 nm,中心5个波长输出功率的平坦度为14 dB。同时,激光器具有灵活的波长可切换特性,通过调整驱动信号和偏振控制器的状态,实现了单波长、双波长、三波长以及更多波长的输出。该激光器可应用于大容量波分复用系统和光纤传感。     

Far infrared optically pumped SO2laser

CO2laser pumping of the SO2molecule has produced far infrared (FIR) lasing on three rotational lines in the ν1excited state. Complete line assignments have been derived for all of the observed transitions.     

Laser4F3/2→4I9/2and4F3/2→4I13/2transitions in KY(WO4)2:Nd3+

We report the observation of lasing at 0.9137 μm and 1.3545 μm in neodymium-doped KY(WO4)2at 77 K. Transition cross sections, fluorescent line width, and branching ratios are given.     

正弦相位调制下多波长掺铒光纤激光器的研究

通过理论分析并实验验证了一种能在室温下实现稳定的掺铒光纤激光器(EDF)多波长输出的方法。通过在线形谐振腔中引入正弦相位调制器。抑制了由于掺铒光纤的均匀展宽效应引起的模式竞争，从而避免了在室温情况下不稳定的单波长激射。与此同时，线形谐振腔引起的空间烧孔效应也有利于抑制均匀展宽效应。通过取样光纤光栅(SBG)的选频作用，实验中观察到稳定的5个波长的同时激射，相邻波长间隔为0．8nm，符合ITU标准。     

Single fundamental mode photonic crystal vertical cavity laser with improved output power

The single fundamental mode output power of photonic crystal vertical cavity lasers is improved by varying sizes of oxide apertures and defect lasing apertures. A maximum output power of 3.1 mW in the fundamental mode has been achieved with a new fabrication process that involves only focused ion beam etching to create holes in selectively oxidised VCSELs.     

Multiwavelength erbium-doped fiber ring laser incorporating an SOA-based phase Modulator

A novel room-temperature multiwavelength erbium-doped fiber (EDF) laser is demonstrated. Stable multiwavelength lasing at room temperature is realized by incorporating a semiconductor optical amplifier (SOA)-based phase modulator in the laser cavity. The SOA is biased below the transparent point with a sinusoidal signal applied to achieve phase modulation, to suppress the homogenous line broadening of the EDF. Stable multiwavelength lasing with wavelengths up to 26 and wavelength spacing as small as 0.19 nm is demonstrated at room temperature.     

掺镱光纤激光器的多波长振荡特性

利用Sagnac梳状滤波器,研究了环形腔掺镱光纤激光器(YDFL)在室温和77 K时的多波长振荡行为。结果表明,在室温和77 K时,掺镱光纤(YDF)均呈现明显的非均匀加宽效应,使得掺镱光纤激光器的起振波长数随抽运光功率的提高而增多。但在室温下,因均匀加宽效应强,掺镱光纤增益的非均匀加宽并不能补偿其内禀不平坦的增益谱,造成波长缺失现象,且当波长间隔减小至0.8 nm时,均匀加宽效应引起的波长竞争造成了多波长振荡的稳定性下降。而在77 K时,掺镱光纤非均匀加宽效应明显增强,在0.8 nm的波长间隔下,无波长缺失现象,将起振波长数增加到32个,且多波长振荡稳定。