摘要:

Spectral line broadening in semiconductor lasers is studied experimentally through the gain saturation characteristics of 1.5 &mgr;m InGaAsP traveling‐wave laser amplifiers. Wide signal gain spectrum under the injection of an intense saturating signal is measured using a weak probe signal. The saturated signal gain spectrum is found to coincide exactly with the unsaturated spectrum under a less biased condition, thus verifying that the semiconductor laser gain saturateshomogeneouslyover the entire gain spectrum. Cross‐saturation characteristics between the two signal channels having identical input powers are also investigated and found to be in good agreement with theoretical calculations based on the homogeneous gain model. The degree of gain saturation is confirmed to be uniquely determined by the total output power from both channels.

ISSN:0003-6951    

DOI:10.1063/1.98424

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Planar and channel optical waveguides have been produced inY‐cut LiTaO3substrates by zinc diffusion from the gaseous phase at 800 °C. Prism coupler measurements on planar waveguides diffused for 6 h indicate effective index changes of 0.0063 and 0.0033 for TE and TM polarizations, respectively, with effective diffusion depths of 3.5 and 3.9 &mgr;m for the two polarizations. Losses in channel waveguides at 0.633 &mgr;m wavelength were 1.0±0.2 dB/cm for TE polarized fields, as compared with 4.7±1.0 dB/cm measured on companion samples produced by the conventional Ti indiffusion process at 1150 °C. Electro‐optic modulation has been demonstrated in channel waveguide interferometers produced by this technique. Based on electron microprobe analysis, a surface Zn concentration of ∼1.3×1021cm−3has been determined.

ISSN:0003-6951    

DOI:10.1063/1.98425

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A modulated stripe width structure (MSW) has been applied to a GaAlAs/GaAs distributed feedback buried heterostructure laser to obtain complete single longitudinal mode oscillation. An MSW device having a gradual modulation scheme and antireflecting films on the cleaved facets has been fabricated using reactive ion etching (RIE). Principal results include realization of a reactive ion etched second‐order grating with the grooves as deep as 0.15 &mgr;m after regrowth and a modulated stripe having extremely fine definition made possible by RIE. The device had a spectrum which agreed markedly well with an analytical result. The effective functioning of the MSW structure has thereby been confirmed experimentally.

ISSN:0003-6951    

DOI:10.1063/1.98426

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We show experimentally that chirped gratings can be used to obtain high coupling efficiencies into waveguides containing media with an intensity‐dependent refractive index.

ISSN:0003-6951    

DOI:10.1063/1.98399

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Polarization bistability between the transverse electric (TE) and transverse magnetic (TM) modes is observed in an external cavity semiconductor laser. Hysteresis in the polarization‐resolved output power is obtained by controlling the optical feedback power of the TE mode via an intracavity electro‐optic modulator. Transitions between single external‐cavity frequencies of TE and TM modes are also demonstrated. Nonlinear gain saturation is the origin of this bistability.

ISSN:0003-6951    

DOI:10.1063/1.98400

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The theory of electron and positron channeling and radiation production in crystals has been extended to macroscopic‐scale systems. The new theory, named QCP theory (quasi‐channeling phenomenon), examines macroscopic systems that exhibit periodicity along the axis of beam propagation, specifically, periodic electrostatic fields; the dimensions of the field periodicity (lz) are much greater than typical interatomic lattice spacing (lL), e.g.,lz≫lL, but much smaller than a typical wiggler wavelengthlw, e.g.,lw≫lz. The feasibility of a laser based on this predicted new phenomenon is examined in this letter. Differences between the properties of the proposed quasi‐channeling radiation and radiation produced by wigglers and free‐electron lasers (FEL’s) are discussed. System lengths a factor of 103shorter than FEL’s are expected, with favorable scaling for below 500 eV laser photon output energies. A 500‐eV QCP laser system with a gain of 1 and a length of 1 m is predicted, based on extrapolations of existing storage‐ring technology.

ISSN:0003-6951    

DOI:10.1063/1.98401

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A new technique for sinusoidal intensity modulation of light at microwave frequencies using a frequency modulated semiconductor laser and an interferometer is described. This technique can be more efficient than direct amplitude modulation and, since sidebands at harmonics of the modulation frequency are generated, is capable of reaching higher frequencies than direct modulation. The highest observed frequency (18 GHz) was generated by direct modulation of a laser diode at 9 GHz, and was limited by the bandwidth of available detectors. Frequencies in excess of 100 GHz can be obtained using suitable detectors.

ISSN:0003-6951    

DOI:10.1063/1.98402

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Second‐order hyperpolarizabilities have been calculated by the three‐level model for systems having low‐energy double transitions. In the three‐level model, the second excited state, in addition to the first excited and ground states, is explicitly taken into account. The second‐order hyperpolarizabilities calculated by the three‐level model gave excellent agreement with the observed values determined by the dc induced second harmonic generation technique, for 4‐aminostilbene,p‐nitroaniline, and 2‐methyl‐4‐nitroaniline.

ISSN:0003-6951    

DOI:10.1063/1.98989

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We have calculated the response of a nonlinear directional coupler fabricated in an AlGaAs/GaAs structure using a realistic model for the optical nonlinearities. The model takes into account carrier‐density‐dependent index of refraction and absorption, and lateral carrier diffusion in each of the two coupled channel waveguides. Our results differ considerably from those obtained using a Kerr model for the optical nonlinearities.

ISSN:0003-6951    

DOI:10.1063/1.98403

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A solid‐state device capable of continuous detection of individual photons in the wavelength range from 0.4 to 28 &mgr;m is described. Operated with a dc applied bias, its response to the absorption of incident photons consists of submicrosecond rise time pulses with amplitudes well above the electronic readout noise level. A counting quantum efficiency of over 30% has been demonstrated at a wavelength of 20 &mgr;m, and over 50% was observed in the visible‐light region. Optimum photon‐counting performance occurs for temperatures between 6 and 10 K and for count rates less than 1010counts/s per cm2of detector area. The operating principle of the device is outlined and its performance characteristics as a photon detector are presented.

ISSN:0003-6951    

DOI:10.1063/1.98404

出版商:AIP    

年代:1987

数据来源: AIP