Room temperature photonic crystal defect lasers at near-infraredwavelengths in InGaAsP

Room temperature lasing from optically pumped single defects in a two-dimensional (2-D) photonic bandgap (PBG) crystal is demonstrated. The high-Q optical microcavities are formed by etching a triangular array of air holes into a half-wavelength thick multiquantum-well waveguide. Defects in the 2-D photonic crystal are used to support highly localized optical modes with volumes ranging from 2 to 3 (λ/2n)³. Lithographic tuning of the air hole radius and the lattice spacing are used to match the cavity wavelength to the quantum-well gain peak, as well as to increase the cavity Q. The defect lasers were pumped with 10-30 ns pulses of 0.4-1% duty cycle. The threshold pump power was 1.5 mW (≈500 μW absorbed)     

Ultralow Lasing Thresholds of$pi $-Type Supermodes in Cyclic Photonic Molecules Composed of Submicron Disks With Monopole and Dipole Modes

Cyclic photonic molecules (CPMs) composed of an even number of identical submicron-size circular-disk active resonators in free space are studied in two dimensions. Cold-cavity lasing frequencies and threshold values of material gain are extracted from an electromagnetic eigenvalue problem with exact boundary and radiation conditions. We show that assembling several small cavities in a tightly packed CPM efficiently lowers the thresholds of optically coupled nonwhispering-gallery modes of the lowest values (i.e., 0 and 1) of the azimuth index in each cavity provided that high antisymmetry is arranged.     

Photonic crystal point-shift nanolaser with ultimate small modal volume

A photonic crystal nanolaser consisting of only the shift of two lattice points was fabricated by HI/Xe inductively coupled plasma etching. The room temperature lasing was observed by photopumping. The three-dimensional finite-difference time-domain calculation showed that the lasing mode has small modal volume close to (/spl lambda//2n)/sup 3/.     

Lasing at bend, branch and intersection of photonic crystal waveguides

The authors report room temperature lasing by pulsed photopumping at line and point composite defects, i.e. a 60/spl deg/-bend, a Y-branch and an intersection of single line defect waveguides, in a GaInAsP photonic crystal slab. The lasing wavelength was different from the simple line defect lasing mode. This indicates that such waveguide components act as microcavities with localised modes.     

二维复周期光子晶体的带隙结构

提出了由二维六边形结构和三角结构叠合构成的复周期光子晶体 ,利用平面波展开法计算了由空气中的介质圆柱棒组成的该复周期光子晶体的带结构。结果表明二维六边形结构和三角结构叠合构成的复周期结构的光子晶体可以形成很宽的TE波光子带隙 ,并且具有较宽的TE波和TM波带隙重叠的绝对光子带隙     

Lasing band-edge identification for a surface-emitting photonic crystal laser

The possibility of single-mode oscillation over a large cavity area for photonic crystal lasers emitting at the photonic band edge has resulted in much interest in such materials for new forms of solid-state laser. In this paper, we measure the photonic bandstructure in our sample and identify the lasing band edge. By mapping out the bandstructure at the /spl Gamma/-point, we have observed fine structure at the band edge. The experimental results are in good agreement with the theoretically predicted bandstructure. Above threshold, we observe a lasing peak at 965 nm at one of the band edges. The far-field distribution of the laser is measured, showing an annular profile and azimuthal polarization. Calculations on the far-field distribution at the lasing band edge suggest the annular profile is due to an anti-symmetric resonant mode.     

Flattening of dynamic dielectric phase grating and single-mode lasing under the conditions of transverse oscillations of luminous flux

Emission spectra and the intensity patterns of InAsSbP/InAsSb/InAsSbP-based diode lasers with different cavity lengths and a spectral range of 3–4 μm were studied. It is ascertained experimentally that a 200-to 300-μm-long and 18-μm-wide laser cavity ensures single-mode lasing, during which the wavelengthdecreases with current by about 100 ? and the top of the intensity pattern becomes bimodal, thus indicating that there are transverse spatial oscillations of laser flux in the cavity. In a 300-to 500-μm-long cavity, several tens of modes are generated mainly on the long-wavelength side of the mode that prevailed initially at the lasing threshold and spatial oscillations of laser flux are not observed. Single-mode lasing is attained due to the fact that the transverse oscillations of laser flux flatten the dynamic dielectric phase grating, which is usually produced by the interaction between lasing modes, and prevent an increase in amplification on the long-wavelength side of the dominant mode. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 36, No. 11, 2002, pp. 1388–1392. Original Russian Text Copyright ? 2002 by Astakhova, Danilova, Imenkov, Kolchanova, Yakovlev.     

Intensity fluctuation in semiconductor lasers coupled to external cavity

Broad peaks are observed in the intensity noise spectrum for external cavity AlGaAs lasers. Oscillating longitudinal mode spectrum measured with a high resolution Fabry-Perot interferometer indicates that the intensity noise peaks result from the lasing of several closely spaced external cavity modes. A new mechanism is proposed to explain the observed noise spectrum; the intensity fluctuation is induced by modulation of the dielectric constant in the semiconductor cavity due to the beating of the electric fields for lasing modes. Qualitative agreements between the theory and experiments are obtained.     

Engineering Symmetry‐Breaking Nanocrescent Arrays for Nanolasing

This paper describes a symmetry‐breaking plasmonic lattice structure that can support narrow resonances as optical feedback for nanolasing. A scalable technique is developed to fabricate nanocrescent arrays with low‐structural symmetry unit cells to achieve in‐plane quadrupolar lattice plasmon modes. These lattice plasmons with extremely narrow linewidths preserve nonzero net dipole moments under normal excitation. Ultrafast band‐edge lasing can be switched on and off by changing the polarization of the incident pump light. The quadrupolar lattice plasmon lasing process is simulated with a semi‐quantum model and the sharp tips on the nanocrescents accelerate the lasing buildup process and enhance stimulated emission.     

多注速调管TM310 模光子晶体谐振腔研究

研究了适用于多注速调管的TM₃₁₀ 模光子晶体谐振腔,发现在此类谐振腔的缺陷中心放置单层光子晶体结构能抑制与主模临近的杂模。进一步研究发现,为了易于工程实现,在不采用光子晶体谐振腔的前提下,在谐振腔中放置单层光子晶体结构,亦能抑制与主模临近的杂模,并能增大主模与非工作模式的频率间隔。利用HFSS 软件对X 波段此类谐振腔进行了模拟计算,验证了该方法的有效性。     

Far- and near-field investigations on the lasing modes intwo-dimensional photonic crystal slab lasers

We present experimental investigations on the lasing modes in two-dimensional (2-D) hexagonal cavities defined by photonic crystals on slab waveguide structures. The far-field emission patterns and near-field intensity distributions of the lasing modes are analyzed in polarization-resolved 2-D angular distribution measurements and spectrally resolved near-field scanning optical microscopy. The far- and near-field analyses result in identification of the various lasing modes and their subsequent classification into one- and two-dimensional modes. In the one-dimensional modes oscillating between two parallel boundaries of the cavities, longitudinal and transverse modes are identified and found to have transverse-electric polarization. In the two-dimensional modes oscillating two-dimensionally in the cavities, various modes including whispering-gallery-like modes are observed and found to exhibit various polarization states     

Characteristics of modified single-defect two-dimensional photonic crystal lasers

The resonant modes found in a modified single-defect two-dimensional photonic crystal slab structure are theoretically and experimentally studied. There exist several modes in the band gap: doubly degenerate (dipole and quadrupole modes) and nondegenerate (hexapole and monopole modes). Among them, the monopole mode specifically attracts our interest because of its nondegeneracy, good coupling with the gain medium, and existence of the intensity minimum at the center of the cavity, which would open up the chance for the electrically driven single-defect laser. The nondegenerate hexapole mode, a special type of whispering gallery mode, has a very high quality factor. We have fabricated two types of modified single-defect lasers, i.e., air-based free-standing and SiO/sub 2/-based epoxy-bonded structures. Rich lasing actions in both structures are experimentally observed under optically pulsed pumping conditions at room temperature. In the free-standing slab structure, photons are strongly confined in vertical direction, and the lasing operations of all resonant modes with low thresholds are obtained. Especially, the nondegenerate monopole-mode laser is confirmed to have a large spontaneous emission factor of >0.06, estimated by analyzing rate equations. In the SiO/sub 2/-based slab structure, thermal properties are improved at the expense of vertical losses.     

Characteristics of Electrically Driven Two-Dimensional Photonic Crystal Lasers

We demonstrate room-temperature low-threshold-current lasing action from electrically driven wavelength-scale high-quality photonic crystal lasers having large spontaneous emission factors by solving the theoretical and technical constraints laid upon by the additional requirement of the current injection. The ultrasmall cavity is electrically pulse pumped through a submicron-size semiconductor “wire” at the center of the mode with minimal degradation of the quality factor. In addition, to better utilize the low mobility of the hole, we employ a doping structure that is inverted from the conventional semiconductors. Rich lasing actions and their various characteristics are experimentally measured in the single-cell and three-cell photonic crystal cavities. Several relevant measurements are compared with three-dimensional finite-difference time-domain computations based on the actual fabricated structural parameters. The electrically driven photonic crystal laser, which is a small step toward a “practical” form of the single photon source, represents a meaningful achievement in the field of photonic crystal devices and photonic integrated circuits as well as of great interest to the quantum electrodynamics and quantum information communities.     

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     

Liquid crystal mirror-based wavelength-tunable laser module with asynchronous mode cavity

We investigated experimentally the impact of the cavity spacing on the lasing mode stability of the external cavity wavelength-tunable laser (ECTL) with Fabry-Pe/spl acute/rot etalon and liquid-crystal-based wavelength-tunable mirror. In the asynchronous mode cavity ECTL, the etalon assists in the suppression of the cavity modes at the neighboring transmission peaks of the lasing wavelength due to the misalignment to the etalon's peak. Therefore, the ECTL with asynchronous mode cavity shows highly mode stable lasing operation. The fabricated ECTL module with optimized asynchronous mode cavity shows excellent lasing property of sidemode suppression ratio more than 59 dB and output power of over 14 dBm for a 45-nm tuning range.     

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.     

Method for Preparation of Semiconductor Quantum‐Rod Lasers in a Cylindrical Microcavity

An efficient method for preparation of semiconductor quantum rod films for robust lasing in a cylindrical microcavity is reported. A capillary tube, serving as the laser cavity, is filled with a solution of nanocrystals and irradiated with a series of intense nanosecond laser pulses to produce a nanocrystal film on the capillary surface. The films exhibit intense room‐temperature lasing in whispering‐gallery modes that develop at the film–capillary interface as corroborated from the spacing detected for the lasing modes. Good lasing stability is observed at moderate pump powers. The method was applied successfully to several quantum‐rod samples of various sizes.     

Analysis of microcavity VCSEL lasing modes using a full-vectorweighted index method

Presents a semi-analytic full-vector method for calculating the spatial profile, optical confinement factor resonant frequency, absorption loss, and mirror loss of lasing modes in cylindrically symmetric microcavity vertical-cavity surface-emitting lasers (VCSEL's). It can be shown that this method gives the best separable approximation for the electric and magnetic vector potentials. Our technique can model the entire VCSEL structure and can treat complex media. We apply the method to etched-post and oxide-apertured VCSEL's designed for 980-nm emission and find a blueshift in cavity resonance as the cavity radius shrinks. We also find a minimum optical cavity radius below which radially bound lasing modes cannot be supported. This radius depends on the device geometry and lies between 0.5 and 1 μm for the devices studied. Once this model is augmented to include diffraction losses-the dominant loss mechanism for conventional small aperture lasers-it will provide a complete picture of lasing eigenmodes in microcavity VCSEL's     

光子晶体调制半导体激光器侧模

为了实现半导体激光器的单侧模稳定工作,提出了一种在激光器的脊条两侧引入光子晶体结构滤除半导体激光器高阶侧模的方法。通过调整激光器上表面的刻蚀深度、光子晶体区域的条宽和间隔来改变激光器内部的模场分布,同时结合选择性的载流子注入来增强基模的激射优势,进而减少侧模的数量。实验上制作了主脊条宽度为6 m,光子晶体周期5 m,波长1 550 nm的半导体激光器。测试结果表明:在连续工作的情况下,电流300 mA的时候,高阶侧模受到抑制,水平发散角变为10.2,证实了光子晶体结构调制激光器侧模的可行性。     

Theoretical calculation of lasing spectra of quantum-dot lasers:effect of homogeneous broadening of optical gain

A theoretical calculation is presented for the effect of homogeneous broadening of optical gain on lasing spectra of quantum-dot lasers. Based on a coupled set of rate equations considering both the size distribution of quantum dots and a series of longitudinal cavity modes, we show that dots with different energies start lasing independently due to their spatial localization when the gain spectrum is a delta-like function, and that the dot ensemble contributes to a narrow-line lasing collectively under large homogeneous broadening. The result explains quite excellently the experimental lasing spectra found in self-assembled InGaAs-GaAs quantum-dot lasers