Waveguide Gain Research Articles

1.7 μm excited state absorption measurement in erbium-doped glasses

We have measured the complete 1.7 μm excited state absorption (ESA) spectrum in erbium-doped glasses. The spectrum is obtained by measuring the gain of an erbium-doped waveguide in the 1400–1800 nm region. Using the measured spectra, we estimate the 1.5 μm uniform upconversion rate by calculating the spectral overlap between the 1.5 μm emission and 1.7 μm ESA cross sections. The technique is applied to erbium-doped, ion-exchangeable silicate glasses yielding upconversion constants in the range of 1–10×10−18 cm3/s.

High-power, diffraction-limited, monolithically integrated master oscillator/power amplifier

Monolithically integrated master oscillator/power amplifiers have been fabricated with a single-mode distributed Bragg reflector laser as the oscillator and a chain of amplifier output couplers defined by a single-mode waveguide gain region and a second-order grating detuned from the gain peak. The output of the amplifier chain is a single frequency and can be phased to obtain a diffraction-limited output up to an output power of 485 mW.

GaInAsP/InP buried-heterostructure surface-emitting diode laser with monolithic integrated bifocal microlens

A new surface-emitting diode laser has been demonstrated, which consists of a buried-heterostructure waveguide gain region on one side of the substrate and a bifocal microlens of 210 μm diameter on the other side. The bifocal microlens is composed of a collimating lens in the center (70 μm diameter) and a spherical mirror in the surrounding region, for output collimation and optical feedback, respectively. Accurate alignment between the gain region and the microlens has been obtained by using the focused light spot produced by the latter. Initial device results show room-temperature pulsed threshold currents around 92 mA (with a low of 70 mA) and far-field patterns with a narrow central lobe of 1.25°.

Anomalous reflection of light from the surface of an amplifying corrugated waveguide

The problem of reflection of light from the surface of an amplifying corrugated waveguide is solved. An increase in the waveguide gain increases considerably the reflection coefficient and reduces the spectral width of the reflection peak.

Linear tailored gain broad area semiconductor lasers

Tailored gain semiconductor lasers capable of high-power operation with single-lobed, nearly diffraction limited beamwidths only a few degrees wide have been demonstrated in proton implanted chirped arrays and halftone broad area lasers. We analyze lasers with a linear gain gradient, and obtain analytic approximations for their unsaturated optical eigenmodes. Unlike a uniform array, the fundamental mode of a linear tailored gain laser is the lasing mode at threshold. Mode discrimination may be controlled by varying the spatial gain gradient. All modes of asymmetric tailored gain waveguides have single-lobed far-field patterns offset from 0°. Finally, we utilize tailored gain broad area lasers to make a measurement of the anti-guiding parameter, and find b = 2.5 \pm 0.5 , in agreement with previous results.

Integrated-optic, narrow-linewidth laser

We report the demonstration of the single-frequency and narrow-linewidth (<100 kHz) operation of an extended cavity laser consisting of a Ti:LiNbO3 single-mode waveguide circuit and an InGaAsP waveguide gain medium. A parallel coupled cavity, electro-optic elements for tuning the resonant frequencies of the cavities, and an external phase modulator are integrated on the lithium niobate crystal.

Approximate formulas for the far field and gain of open-ended rectangular waveguide

Approximate formulas are derived for the far field and gain of standard, open-ended, rectangular waveguide probes operating within their recommended usable bandwidth. (Such probes are commonly used in making near-field antenna measurements.) The derivation assumes first-order azimuthal dependence for the fields, and an <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</tex> -plan pattern given by the traditional Stratton-Chu integration of the transverse electric ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TE_{10}</tex> ) mode. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</tex> -plane pattern is estimated by two different methods. The first method uses a purely <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</tex> -field integration across the end of the waveguide. The second, more accurate method approximates the fringe currents at the shorter edges of the guide by isotropically radiating line sources. The amplitude of the line sources is determined by equating the total power radiated into free space to the net input power to the waveguide. Comparisons with measurements indicate that for <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</tex> -band and larger waveguide probes, both methods predict on-axis gain to about 0.2 dB accuracy. The second method predicts far-field power patterns to about 2 dB accuracy in the region <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">90\deg</tex> off boresight and with rapidly increasing accuracy toward boresight.

Helical distributed feedback gas laser

Hitherto, distributed feedback (DFB) was achieved in dye lasers, in solid state lasers as well as in gas lasers exclusively by linear periodic modulations of refraction index, waveguide cross section and/or gain. In this letter we report on the first experimental realization of a gas laser with a helical DFB waveguide structure. Here, the laser feedback is provided by a nut instead of the usual mirrors or linear periodic DFB modulations.

Perturbation Theory Applied to Gain or Loss in an Optical Waveguide

Perturbation Theory Applied to Gain or Loss in an Optical Waveguide