We explore the influence of grating characteristics on the lasing performance of polymer circular-grating distributed-feedback lasers. A range of circular-grating sizes and profiles were fabricated on a single silica substrate, which was coated with a thin film of the conjugated polymer poly͓2-methoxy-5-͑2'ethylhexyloxy͒-1,4-phenylene vinylene͔. Variations in lasing threshold and surface-emitted slope efficiency were determined as a function of grating outer diameter and duty cycle. The experimental lasing results are compared with predictions from a theoretical analysis based on an adaptation of the transfer matrix method. We find that an outer diameter of at least 200 m is required to minimize the threshold and optimize the surface-emitted slope efficiency. A groove-to-period duty cycle of ϳ25% gives the lowest lasing thresholds by optimizing the in-plane feedback. We also find that the structure of the polymer-air surface varies substantially with substrate duty cycle, which has implications for optimum device design.

We explore the influence of gain localization on the lasing performance of circular-grating distributed feedback ͑CDFB͒ lasers. The effect is studied in an optically pumped CDFB laser resonator based on a waveguide of the conjugated polymer poly͓2-methoxy-5-͑2Јethylhexyloxy͒-1,4-phenylene vinylene͔. Variations in lasing threshold and slope efficiency are determined as a function of the radius of the optical excitation. The experimental lasing results are compared with predictions from a theoretical analysis based on an adaptation of the transfer matrix method. We find that a strong localization of the gain near the center of the CDFB laser can lead to both a substantial reduction in threshold and increase in output efficiency. As the excitation radius changes from a 90 to a 15 m radius, the threshold energy decreases from 5.3 to 0.29 nJ, and the surface-emitted output efficiency increases by an order of magnitude. A simple model is developed that confirms that the significant reduction in threshold can be explained by an enhanced overlap of the population inversion with the resonant mode.

We demonstrate how to construct a simple single-frequency extended cavity diode laser (ECDL) for the undergraduate laboratory using mainly standard opto-mechanical components. This ECDL is operated with both 635 and 670 nm laser diodes. We present three experiments that can be performed using this ECDL, namely spectroscopic studies of iodine, second harmonic generation, and an optical heterodyne experiment using the ECDL with a helium–neon laser.

We describe a compact all-solid-state continuous-wave, singly resonant optical parametric oscillator (SRO) based on periodically poled RbTiOAsO4. The SRO is pumped at 1.064 microm by a Nd:YVO4 laser, which is itself pumped by a 3-W diode laser. Using the intracavity technique produced an oscillation threshold for the SRO of only 1.6 W (diode-laser power). For 3 W of diode pump power some 65 mW was obtained in the (nonresonant) idler (wavelength 3.52 microm). Temperature tuning over the range 10-100 degrees C resulted in tuning ranges of 1.52-1.54 and 3.41-3.54 microm for the signal and the idler waves, respectively. Importantly, relaxation oscillations were absent.

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