S. Fox

Measurement of the facet modal reflectivity spectrum in high quality semiconductor traveling wave amplifiers

We demonstrate that the Hakki-Paoli technique, commonly used for measuring single pass gain in semiconductor lasers, can be modified to measure facet modal reflectivity down to 10/sup -6/ in semiconductor laser amplifiers. We also introduce a new technique based on Fourier and Hilbert transformations of the spontaneous emission spectrum (the SET method) which enhances the signal-to-noise ratio and permits modal reflectivity measurements down to 10/sup -1/. >

1.9-W quasi-CW from a near-diffraction-limited 1.55-μm InGaAsP-InP tapered laser

1.9-W quasi-CW output power with about 80% of the power in the central lobe is obtained from a 1.55-/spl mu/m wavelength InGaAsP-InP MQW tapered unstable resonator laser. This power is found to be emitted in a near-diffraction-limited beam.

Focus and Edge Detection Algorithms and Their Relevance to the Development of an Optical Overlay Calibration Standard

We present results of investigations into optical focus and edge detection algorithms relevant to overlay metrology. We compare gradient energy, standard deviation, contrast and summed intensity of acquired images as focus metrics for bright-field, scanning confocal, and confocal microscopy. For our purposes, gradient energy calculated via Sobel filtering was found to be the best criterion for an autofocus algorithm. We predict, based on theoretical results, that all of the focus algorithm we considered will focus in different heights relative to the object depending on the material properties of the object. Edge detection is accomplished via a window and spline technique for whole image data, and by application of a multiple line regression algorithm for single scan data. Measurements accomplished through these techniques are compared to state of the art scattering and analysis models.

Polarization insensitive 1.55-μm optical amplifier with GaAs delta-strained Ga/sub 0.47/In/sub 0.53/As quantum wells

We report a novel, polarization insensitive, 1.55-/spl mu/m semiconductor optical amplifier grown by solid source molecular beam epitaxy. The active region contains six Ga/sub 0.47/In/sub 0.53/As quantum wells, each containing three tensile strained GaAs delta layers. Simple ridge waveguide devices were fabricated with 8/spl deg/ angled facets. The internal gain is 26.5 dB for both the transverse electric and transverse magnetic polarizations at a wavelength of 1.55 /spl mu/m and an injection current of 375 mA. The polarization sensitivity of the gain is less than 1 dB for a bandwidth of 45 nm, and the gain is nearly flat with a variation of less than 1 dB for a bandwidth of 20 nm. The saturation output power of these devices is 11 dBm. These results are reproducible and comparable to reports from more complex device designs.

High power diffraction limited output from a tapered laser operating at 1.55 /spl mu/m

550 mW quasi-CW output power with 85% of the power in the central lobe is obtained from a 1.55 /spl mu/m wavelength InGaAsP/InP MQW tapered unstable resonator. This power was found to be emitted in a near-diffraction-limited beam.

Practical approach to design and fabrication of antireflection coatings for semiconductor optical amplifiers

We have used a combination of experimental techniques and a numerical method based on a waveguide model to demonstrate low-modal reflectivity antireflection coatings on semiconductor lasers. Our approach does not require a detailed knowledge of the laser layer structure. We have modeled the experimental spectral reflectivities for single- and two-layer antireflection coatings using this approach. This is the first time that a detailed comparison between theory and experiment has been made for two-layer antireflection coatings.

High power near diffraction limited external cavity single-angled facet tapered lasers, tunable from 1.505 to 1.565 /spl mu/m and 0.795 to 0.855 /spl mu/m with high spectral purity

Summary form only given. We have demonstrated the operation of a high power near diffraction limited external cavity QW laser by implementing a single-angled facet curved input preamplifier with wide tuning and high spectral purity at both 1.55 and 0.83 /spl mu/m wavelengths.

High-power flared semiconductor laser amplifiers

A normal incidence tapered laser amplifier is shown to produce more than 4.5 W optical power at 810 nm in a diffraction-limited beam. A new angled-facet tapered laser amplifier has demonstrated as much as 5 W optical power in a diffraction-limited beam at 810 nm with only a few mWs of coupled input power. Angled-facet laser amplifiers exhibit near-ideal Gaussian beam characteristics. More than 1.9 W CW is obtained in a 970 nm angled-facet tapered laser amplifier. A near-ideal beam quality factor M2 is obtained.

Angled-facet high-power diffraction-limited tapered semiconductor amplifier

Summary form only given. Tapered semiconductor amplifiers have successfully demonstrated high-power diffraction-limited emission. So far, all these amplifiers had normal incidence facets coated with antireflection (AR) coating to prevent self-oscillation. In this work, an angled-facet high-power diffraction-limited tapered GaAs-AlGaAs QW semiconductor amplifier operating at 809-nm was realized. Due to the angled facet structure, any residual reflection from the facets is fed back at a small angle with the signal propagation direction.

300-mW diffraction-limited beam from flat-phase-front antiguided master oscillator power amplifier

Semiconductor master oscillator power amplifier (MOPA) devices based on the resonant transmission properties of resonant-optical-waveguide (ROW) antiguided structures are shown to be promising candidates for stable, coherent, high-power sources. A novel mast oscillator for this type of MOPA is proposed: the three-core antiresonant reflecting optical waveguide (ARROW) diode laser. This device is also based on ROW antiguided structures and can easily be integrated with the power amplifier. Three-core ARROW lasers are shown to have large intermodal discrimination against unwanted modes, and when used as the maser oscillator of a ROW-MOPA, a uniform near-field, flat-phasefront, diffraction-limited beam output is obtained. Experimentally, 350 mW diffraction-limited beam operation has been demonstrated in ROW-MOPA devices without extremely low AR coatings.