Mercury cadmium telluride-based resonant cavity light emitting diode

A CdHgTe resonant cavity light emitting diode (RCLED) is proposed as a new infrared emitter. The device is prepared by molecular beam epitaxy on a CdZnTe substrate. A 10.5 periods Bragg mirror is first deposited. The cavity material is made of Cd_0.75Hg_0.25Te and contains a wide well (50 nm) designed to emit at 3.2 μm. The last three periods of the mirror are n-type doped while the cavity material is covered by a thin p-type CdZnTe layer. A gold layer closes the cavity, serving as the second mirror of a Fabry-Perot cavity tuned around 3.18 urn. It also provides an ohmic contact to the p-region. Under forward bias, the emission spectrum displays a narrow peak (8 meV full width at half maximum) corresponding to the cavity resonance. The position and linewidth of this line are independent of temperature. The directivity of the diode is also improved with respect to a conventional emitter, in agreement with theoretical expectations. Taking advantage of the spectral properties of the RCLED a new multispectral device has been fabricated.     

采用快速压电陶瓷调频元件提高染料激光器的频率稳定度

研究了压电陶瓷腔镜及其支架的机械共振,抑制了支架的本征振动,并设计了快速频响压电陶瓷腔镜,其最低共振频率为125kHz,对380-A.染料激光器进行了稳频,使其线宽减少到300kHz(p-p)。     

Single-frequency tunable Sb-based VCSELs emitting at 2.3 /spl mu/m

We present a comparison between two kinds of single-frequency Sb-based semiconductor VCSELs operating at 2.3 /spl mu/m in continuous-wave regime at room temperature. These lasers are studied in view of application to spectroscopy or trace gas detection. Both are based on a molecular beam epitaxy grown half-VCSEL. In the first configuration, a dielectric mirror is deposited on top to form a microcavity, while in the second a concave mirror is used to form an external cavity. The external cavity VCSEL exhibits 5-mW output power, a narrow linewidth (<<20 kHz), and 50-GHz continuous frequency tunability.     

Linewidth Narrowing and Intensity Enhancement of Wavelength Tunable MOLEDs

Microcavity structure consisting of distributed Bragg reflector and metal aluminum mirror is designed. Using tris (8-hydroxyquinoline) aluminum as electron-transport layer and emissive layer, and N, N′-bis (3-methylphenyl)-N, N′-diphenylbenzidine as a hole-transport layer, microcavity organic light-emitting diodes(MOLEDs) are fabricated. Compared to the electroluminescence spectra of non-cavity OLEDs, the linewidth of the MOLEDs is compressed from 75 nm to 7 nm, and the peak intensity enhances by a factor of about 3. When the effective length of the microcavity is modified, resonance wavelength can be selectively scanned over a very wide range of wavelengths that cover almost 140 nm.     

Tuning characteristics of a tunable-single-frequencyexternal-cavity laser

The lasing characteristics of a tunable-single-frequency laser operated in conjunction with a tunable external cavity are investigated. The effect of phase error in the external cavity on the lasing frequency, linewidth, and output power is calculated by deriving the characteristic equation for the FP cavity as a traveling amplifier with an effective mirror concept. The analysis suggests that the diode laser and the external cavity may be successfully tuned open-loop if the feedback strength is appropriate and the tuning nonlinearities in the active and passive cavities are not too severe. This is demonstrated by maintaining a linewidth of 4 MHz while tuning continuously over 34 GHz     

Self-consistent calculation of lasing modes in a planar microcavity

The self-consistent calculation of lasing modes in a microcavity with infinite plane mirrors is presented. The semiclassical theory is used, with rigorous boundary conditions included for Maxwell's equations to describe both the emitter distribution and the cavity reflectors. The concept of gain-guided versus index-guided modes in such structures can be removed within the semiclassical model, as rigorous boundary conditions for both the radiation source and passive cavity can be handled exactly. We present calculated curves showing the angular dependence of various lasing modes on mirror reflectivity and the threshold gain susceptibility dependence on mirror reflectivity and active diameter. The linewidth dependence on the transverse lasing mode is also considered. Limitations of the semiclassical approach as compared to a fully quantum mechanical approach is emphasized     

Impact of planar microcavity effects on light extraction-Part I:basic concepts and analytical trends

We address the long-standing issue of extracting light as efficiently as possible from a high-index material, n⩾2, where as little as 2%-10% of light not suffering total internal reflection is extracted at standard plane faces due to the small critical angle ~1/n. Using a planar microcavity to redirect spontaneous emission toward the surface, constructive interferences can bring 15%-50% of the light out, enhancing brightness and efficiency. In this first of two papers, an approximate approach is used showing the importance of small cavity order m_c and of the m_c/n² ratio. We define a condition for microcavity regime as m_c<2n² . It is shown that most of light extraction is usually attained for moderate mirror reflectivities ~1-m_c/n² typically below 90%, and without strong directionality. Balance between emission directionality, radiance (brightness), and spectral narrowing is discussed. We define a brightness enhancement factor B given by Bm _cΔΩ=4π where ΔΩ is the largest internal solid angle of either the cavity mode or that deduced from the material emission linewidth. Design rules are applied to distributed dielectric mirrors yielding an optimal number of periods. The underlying physical competition between emission into guided modes, Fabry-Perot modes and the so-called “leaky modes” is analyzed     

High quantum efficiency and narrow absorption bandwidth of thewafer-fused resonant In0.53Ga0.47As photodetectors

We demonstrate greater than 90% quantum efficiency in an In_0.53Ga_0.47As photodetector with a thin (900 Å) absorbing layer. This was achieved by inserting the In_0.53 Ga_0.47As/InP epitaxial layer into a microcavity composed of a GaAs/AlAs quarter-wavelength stack (QWS) and a Si/SiO₂ dielectric mirror. The 900-Å-thick In_0.53 Ga_0.47As layer was wafer fused to a GaAs/AlAs mirror, having nearly 100% power reflectivity. A Si/SiO₂ dielectric mirror was subsequently deposited onto the wafer-fused photodiode to form an asymmetric Fabry-Perot cavity. The external quantum efficiency and absorption bandwidth for the wafer-fused RCE photodiodes were measured to be 94±3% and 14 nm, respectively. To our knowledge, these wafer-fused RCE photodetectors have the highest external quantum efficiency and narrowest absorption bandwidth ever reported on the long-wavelength resonant-cavity-enhanced photodetectors     

基于片上微腔自反馈注入锁定的窄线宽激光器

对半导体激光器外腔自反馈注入锁定进行了理论分析,研究了片上微腔的自反馈注入锁定对于分布反馈(DFB)激光器输出线宽的影响,分析了决定锁定带宽及线宽压缩系数的关键参数。基于Q值为2.4×10⁶的片上Si₃N₄微腔的后向瑞利散射实现了DFB激光器的自反馈注入锁定,将其输出线宽由自由运转时的556.71 kHz压窄到了92.28 kHz,锁定带宽达到425 MHz。研究结果有助于理解半导体激光器自反馈注入锁定机理,并为实现窄线宽激光器提供了新的结构更简单、集成化潜力更高的方案。     

Obtaining high efficiency at low power using a quantum-dotmicrocavity light-emitting diode

Efficiencies are calculated for quantum-dot apertured-microcavity light-emitting diodes. Although the maximum efficiency depends strongly on the quantum-dot inhomogeneous broadening, greater than 20% efficiency is calculated for a small-sized apertured microcavity, even for an inhomogeneous linewidth as large as 30 meV. The efficiency can be increased to 40% if the inhomogeneous linewidth is reduced to 10 meV and to more than 60% if the inhomogeneous linewidth is eliminated to leave a homogeneous linewidth of 6.6 meV. The maximum output powers are ~40 nW, although a microarray can increase this value. For the case of a single quantum dot, an efficiency >80% is estimated for a submicron apertured-microcavity, with a maximum output power of ~3 nW     

Electrical properties of manganese doped Ga1−xInxAs grown by liquid phase epitaxy

Mn-doped Ga_1?xIn_xAs crystals (0 < x < 0.25) have been grown by the LPE technique, and the doping characteristics and electrical properties of the layers have been studied by Hall measurement. The distribution coefficient of Mn has been found to depend on the substrate orientation. The acceptor enerby level is about 77 meV and is comparable to that of Mn-doped GaAs. p-n junction diodes with high InAs compositions, grown using the step grading technique, showed a diode factor of 2. Electron diffusion lengths greater than 3μm have been measured in these Mn doped layers.     

Continuous-wave mid-infrared VCSELs

We report the continuous-wave operation of an optically pumped mid-infrared (mid-IR) vertical-cavity surface-emitting laser (VCSEL). The active region consisting of type-II antimonide quantum wells with a “W” configuration occupies a cavity formed by a semiconductor bottom mirror and dielectric top mirror. The emission wavelength of 2.9 μm is nearly independent of temperature (dλ/dT≈0.09 nm/K) compared to type-II edge-emitters and the multimode linewidth is narrow (2.9 nm). At T=78 K, the threshold pump intensity is ≈940 W/cm², the peak output power from a 50-μm spot is 45 mW, and the differential power conversion efficiency is 4.5%. Lasing is observed up to T=160 K     

Diode-pumped and packaged acoustooptically tunableTi:Er:LiNbO3 waveguide laser of wide tuning range

Design, fabrication, and properties of an acoustooptically tunable Ti:Er:LiNbO₃ waveguide laser of up to 31-nm tuning range in the wavelength band 1530 nm<λ<1575 nm are discussed. The laser cavity is formed by an Au mirror and a dielectric mirror as output coupler, both vacuum-deposited on the polished waveguide endfaces. As tunable intracavity wavelength filter with zero frequency shift, two monolithically integrated single-stage acoustooptical TE-TM-mode converters are used together with two polarization splitters operated as TE- and TM-pass polarizers, respectively. The minimum threshold of about 54 mW (coupled) pump power is obtained at λ≈1561-nm emission wavelength for diode laser pumping at λ_p≈1480 nm. With about 110-mW coupled pump power, up to 320-μW output power is achieved; the emission linewidth is 0.3 nm     

Enhancement effect of phase-conjugate waves of third order nonlinear medium in the Bragg microcavity

It is desiredthat the photon mode could be controlledby using photonic crystal ,such as threshold-less laserdevices[1].The key problemin fabricating photonic de-vices is howtointroduce a defect state[2]into a photoniccrystal ,nevertheless it is difficult …     

Fabrication Method,Ferromagnetic Resonance Spectroscopy and Spintronics Devices Based on the Organic-Based Ferrimagnet Vanadium Tetracyanoethylene

Organic-based magnetic materials have been used for spintronic device applications as electrodes of spin aligned carriers and spin-pumping substrates. Their advantages over more traditional inorganic magnets include reduced magnetic damping and lower fabrication costs. Vanadium tetracyanoethylene, V[TCNE]_x (x ≈ 2), is an organic-based ferrimagnet with an above room-temperature magnetic order temperature (T_c ≈ 400 K). V[TCNE]_x has deposition flexibility and can be grown on a variety of substrates via low-temperature chemical vapor deposition (CVD). A systematic study of V[TCNE]_x thin-film CVD parameters to achieve optimal film quality, reproducibility, and excellent magnetic properties is reported. This is assessed by broadband ferromagnetic resonance (FMR) that shows most narrow linewidth of ≈1.5 Gauss and an extremely low Gilbert damping coefficient. The neat V[TCNE]_x films are shown to be efficient spin injectors via spin pumping into an adjacent platinum layer. Also, under an optimized FMR linewidth, the V[TCNE]_x films exhibit Fano-type resonance with a continuum broadband absorption in the microwave range, which can be readily tuned by the microwave frequency.     

Tunable,Grating-Gated,Graphene-On-Polyimide Terahertz Modulators

An electrically switchable graphene terahertz (THz) modulator with a tunable-by-design optical bandwidth is presented and it is exploited to compensate the cavity dispersion of a quantum cascade laser (QCL). Electrostatic gating is achieved by a metal grating used as a gate electrode, with an HfO₂/AlO_x gate dielectric on top. This is patterned on a polyimide layer, which acts as a quarter wave resonance cavity, coupled with an Au reflector underneath. The authors achieve 90% modulation depth of the intensity, combined with a 20 kHz electrical bandwidth in the 1.9–2.7 THz range. The modulator is then integrated with a multimode THz QCL. By adjusting the modulator operational bandwidth, the authors demonstrate that the graphene modulator can partially compensate the QCL cavity dispersion, resulting in an integrated laser behaving as a stable frequency comb over 35% of the operational range, with 98 equidistant optical modes and a spectral coverage ~1.2 THz. This paves the way for applications in the terahertz, such as tunable transformation-optics devices, active photonic components, adaptive and quantum optics, and metrological tools for spectroscopy at THz frequencies.     

硅基法布里—珀罗微腔的室温发光

提出了一种新型基于法布里 -珀罗 (F- P)微腔的发光器件结构 .它采用 PECVD方法制备的非晶硅 /二氧化硅结构作为微腔中的布拉格反射腔 ,非晶碳化硅薄膜作为中间光发射层 ,通过对一维方向光子的限制 ,使发光层荧光强度增强 ,谱线变窄 .通过调节发光层和反射腔膜厚及折射率 ,可以精确控制发光峰位 .实验结果证明该结构可望实现全硅基材料的强室温可见光发射 .     

High finesse, thin active layer, multiquantum well optical bistable device

Optical bistability was observed in a multiquantum well microcavity, with a 500 W/cm/sup 2/ intensity threshold and a 10:1 contrast. The device design enhances the cavity finesse (here up to 250), by increasing the number of layers in the Bragg mirror stacks and simultaneously reducing the active layer thickness (here 3 lambda /2, i.e. 360 nm).<>     

Improved out-coupling efficiency from a green microcavity OLED with a narrow band emission source

A highly efficient green microcavity organic light emitting diode was developed using a tetradentate cyclometalated platinum complex, PtN1N, with an intrinsically narrow emission spectral band (FWHM = 18 nm). Devices employing the narrow band emitter in MOLEDs consisting of a single pair of a high index dielectric, Ta₂O₅, and low index dielectric, SiO₂, exhibited a high peak external quantum efficiency of 33.7% compared to a standard OLED in the same device architecture with a peak external quantum efficiency of 25.6%. We have also found in our study that narrow band emission sources in tuned microcavity OLEDs exhibit larger enhancements in light out-coupling efficiency accompanied by small changes in color with respect to viewing angle compared to broad band emitters which is advantageous in display applications.