Electro-optic characteristics of CdTe at 3.39 and 10.6 µ

The physical characteristics of high resistivity CdTe which are relevant to its use for electro-optic modulation have been investigated at 3.39 and 10.6 µ. The unclamped electro-optic characteristic n0^3r41 of CdTe was found to be 12 × 10^–11 m/V and the absorption coefficient is 0.006 cm^–1. Our measurements indicate that CdTe will be a very important material for electro-optic modulation in the infrared

Infrared Absorption at 10.6 μ in GaAs

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Observations of Parametric Fluorescence and Oscillation in the Infrared

Measurements of infrared optical parametric fluorescence are reported for the first time. Using a pump wavelength of 1.064 µ in LiNbO_3 , observations of the fluorescence power, bandwidth, and angular dependence at 1.63 µ are in good agreement with a plane-wave theory. The operating characteristics of two pulsed, internal, doubly resonant parametric oscillators are also reported and compared with predictions of the fluorescence measurements. With measured thresholds on the order of 400–700 W, the two oscillators provided nearly continuous tuning from 1.51 µ to 3.55 µ with average powers of 6 mW and peak powers of 600 W. These powers represent available pump conversion efficiencies of 10% and 50%, respectively. Oscillating bandwidths were only 10% of the fluorescence bandwidth and ranged from 1.7 cm^(-1) to 45 cm^(-1), depending on the output wavelength. Longitudinal mode structure and multiple pulsing of the oscillators were observed

Parametric oscillator tuning curve from observations of total parametric fluorescence

Measurements of total emitted parametric fluorescence power are presented and used to fix one point on the predicted tuning curve of a parametric oscillator. The method is particularly useful for predicting the tuning curve of infrared pumped parametric oscillators. Experimental results, which verify the usefulness of the technique in a 1.06-μ-pumped oscillator, are presented

Longitudinal-mode control in integrated semiconductor laser phased arrays by phase velocity matching

The spectrum of semiconductor laser arrays with separate contacts is investigated. It is demonstrated that the individual laser currents can be selected such that the array operates in a single longitudinal mode in contrast to the multimode nature of its individual constituents. Moreover, it is possible to tune the lasing frequency by varying the laser currents. Wavelength tuning range of ~50 Å, with tuning rate of ~5 Å/mA, is demonstrated. It is suggested that these spectral features, characteristic of lasers which are coupled in parallel, result from the strong frequency dependence of their spatial mode pattern near the phase-matching frequency of their coupled waveguides

Recent Developments In Monolithic Phase-Locked Semiconductor Laser Arrays

Coherent combination of the power of several semiconductor lasers fabricated on the same substrate has been the subject of an intense research effort in recent years, the main motivation being to obtain higher power levels than those available from a single laser in a stable radiation pattern. Best results reported so far include 2.6 Watts cw emitted power and less than 10 far-field angle (in the array plane) in arrays where all the lasers are electrically connected in parallel. A different type of coherent array, where each element has a separate contact, has been recently demonstrated. While requiring the more complex two-level metallization technology, applying a separate contact to each laser provides an additional degree of freedom in the design and the operation of monolithic arrays. The separate contacts can be employed to tailor the near-field and far-field distributions and to compensate for device-to-device nonuniformities. Furthermore, the control of the currents of the array elements allows the performance of a variety of other functions, such as beam scanning, spectral mode control, wavelength tuning and control of the mutual coherence between array elements

Controlled fundamental supermode operation of phase-locked arrays of gain-guided diode lasers

Uniform semiconductor laser arrays tend to oscillate in a superposition of their supermodes, thus leading to large beam divergence and spectral spread. Discrimination among the supermodes in phase-locked arrays is discussed theoretically. It is shown that supermode discrimination in gain-guided arrays, in favor of the fundamental supermode, is made possible by the near-field interference patterns which result from the complex optical fields of the gain-guided lasers. A fundamental supermode operation is demonstrated, for the first time, in GaAlAs/GaAs gain-guided laser arrays. This is achieved by control of the current (gain) profile across the array by means of individual laser contacts

Ultrabright Backward-wave Biphoton Source

We calculate the properties of a biphoton source based on resonant backward-wave spontaneous parametric down-conversion. We show that the biphotons are generated in a single longitudinal mode having a subnatural linewidth and a Glauber correlation time exceeding 65 ns.Comment: 4 pages, 3 figure

Frequency response of intracavity laser coupling modulation

A resonant energy coupling between the atomic system and the oscillating optical mode leads to severe output distortion in intracavity laser coupling modulation. This anomalous behavior, which places a lower limit on the modulation frequency, is investigated in a case of a CO2 laser and compared with theoretical predictions