半导体的CO2激光退火和合金化

本文主要研究连续CO₂激光对半导体的照射效应。实验结果与理论分析说明,用连续CO₂激光照射可将半导体样片加热到所需的温度。与其它短波长的激光不同,波长为10.6μm的连续CO₂激光照射半导体有如下特点:CO₂激光是借助于自由载流子吸收与半导体耦合;样片在深度方向被均匀加热;激光背面照射可以增强退火效果。连续CO₂激光照射可以固相外延再生长的方式使As离子注入Si的损伤层退火恢复。在再生长的过程中注入的As离子进入替位,电激活率很高,而且不发生杂质再分布。将连续CO₂激光背面照射成功地应用于GaAsFET制备欧姆接触,既可避免激光正面照射对器件结构的破坏,又能得到比热退火为好的电学性能。 关键词：     

Far-infrared two-photon intraband transitions in n-InSb

Two-photon cyclotron resonance and two-photon shallow donor transitions have been excited by a high power pulsed D₂O laser emitting λ = 119 μm and 66 μm laser lines at the same time. Transitions involving the absorption of two 119 μm photons or simultaneously one 119 μm and one 66 μm photon were observed. Two-photon selection rules are discussed by a rigorous treatment of the symmetry of the free electron Hamiltonian.     

Coherent transverse speckle dynamics in the case of probing of stationary bulk scattering media by a laser with frequency deviation

A coherent transverse dynamics of scattered speckle fields that arises upon propagation of tunable laser radiation through stationary optically inhomogeneous bulk media has been discovered. The dynamic photochromic speckle effect can be observed experimentally if the deviation of the laser radiation frequency is comparable with or greater than the effective phase delays arising upon scattering of waves in a random or partly organized medium. It was found experimentally that, with an increase in the frequency tuning range of a probing laser diode (λ = 650 nm) or a compact YAG:Nd laser (λ = 532 μm), which can reach hundreds of gigahertz for multiply scattering bulk media from several millimeters to two centimeters thick (fluoroplastic phantoms), the two-dimensional correlation coefficient of speckle structures decreased monotonically, and the characteristic drop for thicker structures was observed at smaller frequency detunings.     

Reflection and scattering from laser-irradiated solid targets at a wavelength of 0.44 μm

Studies of the reflectivity and spectral behaviour of the light scattered from plane solid targets irradiated with the third harmonic of the iodine laser (λ = 0.44 μm) in the intensity range 10¹² to 10¹⁵ W/cm² are reported. The complex spectra of the scattered light observed with normally and obliquely incident laser light provide evidence of stimulated scattering processes. The results are compared with current theories on stimulated Brillouin scattering.     

Possible Mechanism of Infrared Radiation Reception: The Role of the Temperature Factor

Technical Physics - The role of the temperature factor in the mechanism of reception of the CO2 laser low-power infrared (IR) radiation (λ = 10.6 μm) by a sensory neuron membrane has been...     

Thermally induced optical bistability in CdHgTe

We report optical bistability in a room temperature, uncoated Cd_0.185Hg_0.815Te etalon using a cw CO₂ laser at 10.6 μm. The results are consistent with a band gap resonant, dispersive nonlinearity induced by a thermal shift of the band gap energy through interband and free carrier absorption. A refractive index temperature coefficient, dn/dT ～ ? 1 × 10^-3K^-1 was measured, and bistability was observed at incident powers of 20 mW.     

Filtration of partially coherent optical radiation by means of multiphonon Bragg diffraction

The filtering properties of three-phonon acousto-optical Bragg diffraction for increasing the degree of coherence of a partially coherent optical field are investigated by the example of multiphonon acousto-optical interaction in a TeO₂ single crystal. Two possible mechanisms of coherent scattering upon the formation of the highest orders are taken into account. It is shown that the three-phonon interaction is more efficient by at least a factor of two than any mode of one-phonon diffraction realized at the same frequency and the same acousto-optical interaction length. The experimental investigation, using partially coherent radiation of a He-Ne laser (λ = 0.63 μm) diffracted from a transverse acoustic wave propagating in a TeO₂ single crystal, on the whole confirmed the basic theoretical foundations.     

Free carrier absorption in quantizing magnetic fields: Nonpolar optical phonon scattering

A quantum theory of free carrier absorption in nondegenerate semiconductors and in strong magnetic fields which was previously developed to treat the case when acoustic phonon scattering dominates the free carrier absorption process [1] is extended to treat the case when nonpolar optical scattering is important. When the electromagnetic radiation field is polarized parallel to the direction of the applied magnetic field, results are obtained which are similar to those when acoustic phonon scattering is dominant. The free carrier absorption is an oscillatory function of the magnetic field which on the average increases in magnitude with the magnetic field. However, more structure in the free carrier absorption occurs when nonpolar optical phonon scattering dominates. This is due to the fact that there are two periods in the oscillatory magnetic field dependence associated with the emission or the absorption of optical phonons during the intraband transitions. When the cyclotron frequency exceeds the sum of the photon and optical phonon frequencies, i.e. ω_c > θ + ω_o, the free carrier absorption is predicted to increase linearly with magnetic field when ?ω_c? k_BT. The magnetic field dependence of the free carrier absorption can be explained in terms of phonon-assisted transitions between the various Landau levels in a band involving the emission and absorption of optical phonons.     

Transport properties of photo-excited carriers in slightly compensated Hg0.785Cd0.215Te

Photo-Hall measurements are presented for slightly compensated n-type Hg_0.785Cd_0.215Te at 4 K where the electron mobility is limited by charged scattering centers. Using a 10.6 μm laser as the optical source, we observe that the electron mobility passes through a maximum as a function of photo-excited carrier density. Mobility expressions based on the Kane-band model are modified to incorporate neutralization of charged scattering centers by photo-excited carriers. Calculated mobility values are found to be in satisfactory agreement with the data. The observed decrease in mobility for high carrier densities is attributed to electron-hole scattering. The mobility enhancement at lower carrier densities is explained in terms of neutralization of charged acceptors.     

Development of 385-μm D2O laser for plasma diagnostics

An optically-pumped 385-μm D₂O laser has been constructed for Thomson scattering ion temperature measurements in tokamak plasma. Stable single mode and stable tunable (over ±1 GHz) operation of the pump 9R (22) TEA CO₂ laser is performed by using an intracavity ZnSe etalon which is temperature-controlled within ±0.01°C. The saturation broadening with D₂O absorption line is observed for the first time using the tunable 9R (22) CO₂ laser. The pressure broadening coefficient of the N₂O absorption line is measured to be 7.6 MHz/torr using the ±1 GHz tunable 385-μm D₂O Raman laser. At 385 μm, an output quantum efficiency as high as 21% is obtained.     

A new type of intense CO2 laser induced electron emission from a gold surface

We describe the first experimental demonstration of a strong, short duration electron emission from a gold surface irradiated by an intense nanosecond CO₂ laser pulse (λ = 10.6 μm). The emission can neither be explained by multiphoton photoeffect, nor by pure thermionic emission. We interpret it as a dynamic optical field emission process.     

Growth of high quality non-linear optical crystal zinc germanium phosphide for Mid-infrared optical parametric oscillator

ZnGeP₂ single crystals were grown from Vertical Bridgman method. High-quality near-stoichiometric ZnGeP₂ single crystals were obtained in the diameter of 30 mm and length of 120 mm. The results showed that after thermal annealing of the crystals the optical absorption coefficient was below 0.03 cm^?1 at 2.05 μm, and ～0.02 cm^?1 at 3–8 μm. The low absorption loss ZnGeP₂ samples with dimension of 6 × 6 × 18 mm³ were cut from the annealed ingots for 3–5 μm optical parametric oscillation (OPO) experiments. For OPO experiment, we obtained up to 8.7 W output in the 3–5 μm wavelength range (with signal of 3.80 μm and idler of 4.45 μm, respectively) pumped by a 16.3 W 2.05 μm Tm,Ho:GdVO₄ laser at pulse repetition rate of 10 kHz, which corresponded to a conversion efficiency of 53.4% and slope efficiency of 64.8%, respectively.     

Optical properties of sapphire in its opacity range

We have studied the reflection spectrum of leucosapphire in the range of 2.5–25.0 μm. Based on the analysis of the known frequency and temperature dependences of the absorption coefficient in the range of 2.5–7.0 μm, its extrapolation to the range of 10.6 μm has been performed. We have shown that the absorption coefficient in the range of 10.6 μm and in the temperature interval 300–2300 K can be evaluated as β = (2–3) × 10⁴ cm^–1. It has also been shown that the value of this characteristic correlates with the results of investigations of the action of a powerful radiation pulse of a СО₂ laser on the surface of anodized aluminum. These data can be used in the development of technologies of laser processing of articles made of sapphire and ceramics based on aluminum oxide, as well as anodized articles made of aluminum alloys.     

激光对半导体材料损伤的机理研究

研究了半导体材料对激光的吸收机制。运用一维热传导方程以及载流子耦合扩散方程研究了激光与半导体材料相互作用的热输运、自由载流子输运过程。分析了半导体材料的热学损伤、力学损伤,以及光电探测器的击穿损伤机制。应用数值模拟的方法对Nd:YAG脉冲激光(1.06μm)辐照下感兴趣的半导体材料PbS内部瞬时温度场分布进行了模拟。     

A CW DCN waveguide laser of high volumetric efficiency

This paper describes a CW submillimeter waveguide laser operating on 190 and 195 μm DCN lines with high volumetric efficiency. The laser cavity is a 3.2 cm inner diameter, 70 cm long, Pyrex tube with plane reflectors (one of them is a copper mesh) against its ends. After optimization of various parameters (such as the N₂:CD₄:He gas mixture, the pressure and the discharge current, the wall temperature and the output coupling), this laser, with only 57 cm long active discharge, delivers 8.4 and 7.6 mW on the 190 and 195 μm lines, respectively, for the EH₁₁ mode. This represents volumetric powers of 75 and 65 μW cm^-3. The free space propagation of the EH₁₁ fundamental mode was found to be as for a gaussian beam, and the absorption of the laser beam in the atmosphere was also measured.     

Raman spectroscopy of gold nanoparticles in polycrystalline LiF film

Results of the Raman spectroscopy analysis of a new composite material based on a thin polycrystalline LiF film containing gold nanoparticles are presented. The formation of spherical gold nanoparticles in the film has been confirmed by the X-ray structural analysis and observation of the optical plasmon resonance absorption spectrum with a maximum at 534 nm. The obtained composite layers have been subjected to annealing by ruby laser (λ = 694 nm) in the spectral region on a descending long-wavelength wing of the plasmon absorption band of gold nanoparticles. Raman spectroscopy has been applied for the first time to the investigation of the modification of the shape of gold nanoparticles in LiF during laser annealing. The experimental Raman spectra are compared with calculated modes of in-phase bending vibrations generated in gold nanoparticles.     

Generation of mid-IR radiation in near-IR semiconductor lasers based on low-dimensional heterostructures

A method for generating mid-IR radiation (λ ～ 10μm) in near-IR (λ ～1 μm) quantum-well semiconductor heterolasers has been proposed. This method is based on the formation of population inversion at a mid-IR intersubband transition as a result of the depletion of its lower level by a strong near-IR field. In contrast to the previous investigations of this problem, the inhomogeneous broadening of the noted transition (caused by the dependence of its frequency on the carrier energy) is taken into account, and it is proposed to invert it not in the entire spectral range but only in the region resonant with the mid-IR field. This approach makes it possible to significantly reduce (in comparison with the previous estimates) the threshold pump current density for initiating mid-IR generation and, as a result, hope to implement operation of the proposed laser at room temperature in the cw mode.     

Specific features of the magnetoreflection of co-based amorphous ribbons in the IR region

The light reflection spectra and the magnetorefractive effect in the cobalt-based amorphous ribbons in the IR spectral region (λ = 2.5–25 μm) are studied. These amorphous alloys are characterized by the magnetoimpedance effect, which is enhanced after thermal and laser annealing. It is found that the magnetoimpedance and magnetorefractive effects correlate with each other. The magnetorefractive effect reveals a feature at λ = 15–20 μm and the change of sign in the wavelength region 20–25 μm. It is shown that, in the first approximation, the optical properties of the amorphous alloys in the IR spectral region can be explained on the basis of a modified Hagen-Rubens relation. It is found that the change in the reflection coefficient of amorphous metal films in the IR spectral region under action of a magnetic field is caused by the change in both their magnetic permeability and conductivity, which is caused by the degree of polarization of localized electronic states at the Fermi level.     

IR absorption in p-type pb0.97Sn0.03Se

IR absorption in p-type melt grown Pb_0.97Sn_0.03Se crystals is reported. The results for the room temperature absorption coefficient (α) in the wavelength region 2–15 μm are analysed. The indirect absorption edge is found to be at 0.26 eV for this ternary alloy. In the longwavelength region α is found to be proportional to λ², in agreement with the classical free carrier absorption expression. The conductivity effective mass of holes is found to be 0.067 m₀ at 300°K.     

电子辐照对掺铒单模光纤损耗特性的影响

本文介绍了掺铒(Er³⁺)单模光纤电子辐照特性,测量了辐照前后和退火后的光纤参数。发现在0.80-1.60μm范围内辐照引起的损耗很大,在0.80-1.20μm短波部分辐照损耗遵循L_UV=0.342exp[E/0.166];而1.20-1.60μm长波部分遵循L_IR=2.2·10⁴exp[-6.08E](E的单位为eV)。120℃退火60h可使长波辐照损耗减少,但0.80μm附近的损耗反而增加。最后讨论了辐照损耗的机理 关键词：