Three-dimensional superprism effect in photonic-crystal slabs

This paper presents a numerical study of the superprism effect in photonic-crystal (PC) slabs. A fully vectorial three-dimensional time-domain code allows to simulate, with virtually no approximations, the role of the sample finiteness in the dispersive response of the frequency-banded structure. Out-of-plane coupling and transmission of the device are investigated.     

Bandpass resonant filters in photonic-crystal waveguides

A precise and effective technique for the design of bandpass resonant filters realized in a one-missing-row photonic-crystal waveguide by inserting proper defects along the waveguide is proposed. The main characteristics of photonic-crystal-based resonant filters are discussed and an application as channel-dropping filter is presented.     

光子晶体光纤的色散特性

本文用有效折射率模型 ,分析了光子晶体光纤的色散特性 ,定量给出了光子晶体光纤双折射特性与光纤参数之间的关系 ,指出了光子晶体光纤具有多个零色散波长 ,对相关现象作出了合理的解释。     

Band-edge line-up in GaAs/GaAsN/InGaAs heterostructures

Triple GaAs/GaAsN/InGaAs heterostructures were grown by MBE on GaAs substrates, and their optical properties were studied. The band-edge line-up in GaAs/GaAsN and InGaAs/GaAsN heterostructures was analyzed by correlating the experimental photoluminescence spectra with the known parameters of the band diagram in (In,Ga)As compounds. It is shown that a GaAs/GaAsN heterojunction is type I, while an In_xGa_1?x As/GaAsN heterojunction can be type I or type II, depending on the In content x.     

Far-infrared lasing in ruby

The feasibility of submillimeter wavelength (870 GHz) lasing in Al2O3is discussed. The proposed scheme is based on the pumping of the2bar{A}level of ruby via a ruby laser operating on its R2line. Lasing is expected on the2bar{A} rightarrow bar{E}transition of the split²Elevel.     

Beam quality of photonic-crystal fibers

In this paper, we investigate the beam quality of photonic-crystal fibers (PCFs) with one, three, and seven missing airholes. The beam quality factor M/sup 2/ of a PCF is generally larger than unity, even if it is single mode. The results are especially important for the design and measurements of single-mode PCF lasers. A comparison between an M/sup 2/ measurement of the laser beam and the reported numbers can establish whether a PCF laser is operating as single mode or is contaminated by higher order modes.     

Confinement losses and optimization in rectangular-lattice photonic-crystal fibers

Confinement losses in highly birefringent rectangular-lattice photonic-crystal fibers (RLPCFs) are investigated by the multipole method. The losses are strongly polarization dependent, which is due to the anisotropic properties of the cladding. The feature is applied to construct a new kind of single-polarization single-mode photonic-crystal fibers (PCFs), which is based on large differential loss between the two polarizations of the fundamental mode. Furthermore, it is found that the birefringence of RLPCFs is determined mainly by the air holes near the defect core. Consequently, a sandwiching (between triangular structures) rectangular configuration that has the property of reducing leakage loss while simultaneously retaining the birefringence of RLPCF is proposed.     

Low-threshold lasing in novel microdisk geometries

We have fabricated arrays of semiconductor microdisks with diameters from 3.5-9 /spl mu/m using wet chemical etching in combination with epitaxial lift-off and metallic bonding techniques. The microdisks are supported on glass for higher optical confinement and to allow novel annular geometries. The optically pumped microdisks have high-Q (>2000) modes, low-pump thresholds (<20 /spl mu/W) and multimode lasing at liquid nitrogen temperatures. Successive modes are excited by temperature tuning the bandgap.     

Ultralow-threshold-current lasing in inversion channel lasers

A new regime of semiconductor laser operation was observed in quantum-well inversion channels of double heterostructure optoelectronic switches. The quantum-well active region operated with substantial excess negative charge imbalance due to the proximity of a high-density depleted donor charge sheet. Threshold current densities as low as 15 A/cm² in as-cleaved 400-μm-long devices were measured, and unusual high-frequency operation under low power operation was observed. These qualities may be of great significance for optical interconnections and optoelectronic integrated circuits     

双模光子晶体光纤的模间干涉效应

本文用有效折射率模型,分析了双模光子晶体光纤的模间干涉特性,理论结果与实验测量符合得相当好,并且预言了模间于涉精细结构的存在,对相关的高精度测量具有重要的应用价值。     

Design of photonic-crystal and wire waveguide interface

The coupling of light between wire-dielectric and photonic-crystal waveguides, characterized by a triangular lattice of air holes, is investigated through a finite-element time domain (FE-TD) approach, in order to optimize the transmission spectrum. The displacement of the inner-hole rows of the photonic-crystal waveguide, on both sides of the interface, has been shown to considerably improve the coupling, resulting in transmission values higher than 90% and 95% over bandwidths of hundreds of nanometers around 1550 nm. The new design approach is successfully proposed for input and output waveguides with width equal to /spl radic/3/spl Lambda/, as well as for larger widths, like 2/spl radic/3/spl Lambda/ and 3/spl radic/3/spl Lambda/, with /spl Lambda/ being the period of the photonic crystal.     

Polariton lasing in Mie-resonant perovskite nanocavity

Deeply subwavelength lasers(or nanolasers)are highly demanded for compact on-chip bioimaging and sensing at the nanoscale.One of the main obstacles for the development of single-particle nanolasers with all three dimensions shorter than the emitting wavelength in the visible range is the high lasing thresholds and the resulting overheating.Here we ex-ploit exciton-polariton condensation and mirror-image Mie modes in a cuboid CsPbBr3 nanoparticle to achieve coherent emission at the visible wavelength of around 0.53 μm from its ultra-small(≈0.007 μm3 or ≈λ3/20)semiconductor nanocav-ity.The polaritonic nature of the emission from the nanocavity localized in all three dimensions is proven by direct com-parison with corresponding one-dimensional and two-dimensional waveguiding systems with similar material parameters.Such a deeply subwavelength nanolaser is enabled not only by the high values for exciton binding energy(≈35 meV),re-fractive index(>2.5 at low temperature),and luminescence quantum yield of CsPbBr3,but also by the optimization of po-laritons condensation on the Mie resonances with quality factors improved by the metallic substrate.Moreover,the key parameters for optimal lasing conditions are intermode free spectral range and phonons spectrum in CsPbBr3,which govern polaritons condensation path.Such chemically synthesized colloidal CsPbBr3 nanolasers can be potentially de-posited on arbitrary surfaces,which makes them a versatile tool for integration with various on-chip systems.     

The lasing mechanism in fast-wave devices

This brief shows that ac space-charge effects lead to beam instabilities and to a lasing mechanism taking place in fast-wave devices.     

Multipump flattened-gain Raman amplifiers based on photonic-crystal fibers

Raman amplifiers based on photonic crystal fibers, whose cross section can be designed to enhance the nonlinear properties, have been investigated in this work. The use of multiple pumps is studied in order to flatten the amplifier gain spectrum, by varying their number, power, and wavelength, yielding a flatness as low as 0.5 dB in the wavelength range between 1540 and 1572 nm.     

Design optimization for high-brightness surface-emitting photonic-crystal distributed-feedback lasers

A new time-domain Fourier-Galerkin (TDFG) theory is developed to simulate the near-field, far-field and spectral characteristics of surface-emitting photonic-crystal distributed-feedback (SE PCDFB) lasers. It is found that a properly-designed two-dimensional hexagonal or square-lattice grating should efficiently couple the output into a single SE mode that retains coherence for aperture diameters of up to /spl ap/1 mm. We identify lattice structures and precise conditions under which all components of the transverse electric or transverse magnetic polarized optical fields constructively interfere to produce a single-lobed, near-diffraction-limited circular output beam. The TDFG simulations predict that quantum efficiencies as high as 30% (60% if reflectors are built into the waveguide structure) should be attainable. A surprising conclusion is that diffractive coupling into the surface-emitting direction must be relatively weak, in order to assure selection of the desired symmetric in-phase mode. Furthermore, gain media with a moderate linewidth enhancement factor should produce the best SE PCDFB performance, whereas edge emitters nearly always benefit from a very small value.     

管状激光介质的热透镜效应

从理论上详细分析了管状激光介质的热透镜效应,提出了“热感应光线轴”的观点,推导出确定管状激光介质光学性质的折射率分布、二维光线矩阵和热透镜焦距。     

InGaAs submonolayer quantum-dot photonic-crystal LEDs for fiber-optic communications

An InGaAs submonolayer (SML) quantum-dot photonic-crystal light-emitting diode (QD PhC-LED) with for fiber-optic applications is reported. The active region of the device contains three InGaAs SML QD layers. Each of the InGaAs SML QD layers is formed by alternate depositions of InAs (<1 ML) and GaAs. A maximum CW output power of 0.34 mW at 20 mA has been obtained in the 980 nm range.     

Continuous-wave lasing of hybrid lasers

The continuous-wave (CW) lasing of hybrid lasers, which contain a broad-band inhomogeneously broadened laser medium and a narrow-band homogeneously broadened laser medium in a single cavity, is analyzed theoretically. The interactions of the laser modes and two gain media are solved self-consistently using the coupled rate equations. The spectral, gain, and power characteristics under different gain conditions are simulated. It is shown that a small gain from a second narrowband laser medium can effectively shape the lasing spectrum and improve the spectral concentration of the hybrid laser. The total saturated gain profile of the hybrid laser is relatively smooth, due to saturation of the gain of the narrow-band medium to a smaller and below-threshold level     

Band-edge aligned quaternary carrier barriers in InGaAs-AlGaAshigh-power diode lasers for improved high-temperature operation

A new type of band-edge aligned carrier barrier is introduced into InGaAs-AlGaAs single quantum-well (SQW) high-power diode laser structures in order to prevent thermionic emission and the overflow of carriers at elevated operating temperatures. These barriers, which are located in the direct vicinity of the active zone of the laser, are undoped to avoid free-carrier absorption. An InGaAs-AlGaAs SQW laser structure with a 10-nm-thick AlGaAsSb electron-blocking layer on the p-side of an In_0.2Ga_0.8As quantum well was realized. The composition of this layer was adjusted so that its valence-band edge matches that of the adjacent AlGaAs waveguide layer. This is to prevent any additional voltage drop or series resistance due to the injection of holes into the quantum well through the electron blocking layer. These lasers show a high characteristic temperature T ₀ of about 225 K for 1500-μm-long as-cleaved devices, which is about 60 K higher than the same laser structure without the blocking layer. Simultaneously low internal losses (α_i≈1.5 cm^-1 at 20°C) and high internal quantum efficiencies (η_i≈93% at 20°C) are achieved. No additional voltage drop or series resistance was measured. The higher temperature stability is mainly attributed to the suppression of carrier leakage and a reduced free-carrier absorption at elevated temperatures     

3-D photonic-crystal heterostructures: fabrication and in-line resonator

A heterostructured photonic-crystal functional chip consisting of a resonator and waveguides is fabricated by a simple "autocloning" process. First, we prepare a substrate with different corrugation patterns by electron beam lithography and dry etching, and Ta/sub 2/O/sub 5/-SiO/sub 2/ multilayers are successively formed upon the substrate. An in-line resonator is fabricated and characterized by fiber-in-fiber-out measurement, and a resonance peak with Q=270 is demonstrated. The future outlook for the technology is also discussed.