Linewidth and alpha-factor of detuned-loaded DBR lasers

The authors report measurements of the α-factor and linewidth of DBR (distributed Bragg reflector) lasers fabricated with weak grating constants. Such devices exhibit detuned-loading effects, and the measured values depend strongly on the tuning current of the Bragg section. α-factor behavior is found to agree with earlier theoretical predictions. Linewidth behavior is shown to be dominated by carrier shot noise in the tuning section. A theoretical analysis of the DBR laser is outlined including detuned loading and carrier shot noise effect     

Cascaded wavelength conversion by four-wave mixing in a strained semiconductor optical amplifier at 10 Gb/s

We demonstrate for the first time cascaded wavelength conversion by four-wave mixing in a semiconductor optical amplifier. Bit-error-rate performance of <10/sup -9/ at 10 Gb/s is achieved for two conversions of up to 9 nm down and up in wavelength. For two wavelength conversions of 5 nm down and up, a power penalty of 1.3 dB is measured. A system of two wavelength converters spanning 40 km of single-mode fiber is also demonstrated.     

Analysis of injection-locked gain-guided diode laser arrays

A new model for injection-locked gain guided laser arrays is proposed. Diffraction-limited and single-lobe operation of injection-locked arrays is attributed to coherent summation of several transverse modes that are phase locked by injection. The model predicts far-field and near-field patterns, locking bandwidth, beam-steering properties, and locked output power. The effects of varying the master power, beam shape, position, and incidence angle on the slave array facet are also studied. Theoretical and experimental results are compared     

Wavelength conversion by four-wave mixing in semiconductor opticalamplifiers

Time-resolved spectral analysis is performed on 10 Gb/s signals wavelength converted by four-wave mixing (FWM) in semiconductor optical amplifiers. A pattern-dependent chirp resulting from parasitic gain modulation by the signal is measured and characterized as a function of the converter's pump-to-probe ratio. This chirp is found to be insignificant for pump-to-probe ratios exceeding 9 dB     

Efficient diffraction-limited beam combining of semiconductor laserdiode arrays using photorefractive BaTiO3

Beam combining of 820-nm-wavelength laser diodes using two-wave mixing in BaTiO₃ is reported. Energy transfer efficiencies up to 80% were obtained with an index-guided diode. Efficient beam combining of two injection-locked laser arrays was demonstrated. Nearly 100 mW power in a diffraction-limited beam was obtained on the combined beam. Crystal response time of the order of a few seconds was measured     

Wavelength conversion for WDM communication systems using four-wavemixing in semiconductor optical amplifiers

Four-wave mixing (FWM) in semiconductor optical amplifiers is an attractive mechanism for wavelength conversion in wavelength-division multiplexed (WDM) systems since it provides modulation format and bit rate transparency over wide tuning ranges. A series of systems experiments evaluating several aspects of the performance of these devices at bit rates of 2.5 and 10 Gb/s are presented. Included are single-channel conversion over 18 nm of shift at 10 Gb/s, multichannel conversion, and cascaded conversions. In addition time resolved spectral analysis of wavelength conversion is presented     

High-power low-divergence semiconductor lasers for GaAs-based980-nm and InP-based 1550-nm applications

High-power diode lasers with low-vertical divergence and high-fiber coupling efficiency were developed for GaAs-based 980-nm pump lasers and InP-based 1550-nm Fabry-Perot and distributed-feedback (DFB) lasers. Narrow divergence at 980 nm was made possible by a large optical-mode waveguide design, with full-width at half-maximum (FWHM) far-field angles of 11.7°×17.8° and coupling efficiency of 80% into a cleaved single-mode fiber (SMF). A vertical taper processing technique was developed for InP-based laser structures. Fabry-Perot lasers produced over 90-mW output power, 17°×16° FWHM beam divergence angles, and 63% coupling efficiency into a lensed SMF. The vertical taper was successfully integrated in 1550-nm DFB lasers, and over 80 mW single-mode output power with beam divergence angles of 12°×14° was obtained     

8-wavelength DBR laser array fabricated with a single-step Bragggrating printing technique

An 8-wavelength distributed Bragg reflector (DBR) array for narrow channel wavelength division multiplexing (WDM) has been fabricated with a new technique for printing first-order Bragg gratings using a phase mask and a conventional incoherent source. All the distributed gratings were printed in a single photolithographic step with a slightly modified mask aligner. The DBR's excellent wavelength control for channels separated by as little as 0.8 nm is described. Many advanced photonic devices relying on gratings like quarter-wave shifted distributed feedback (DFB) lasers and wavelength division multiplexing (WDM) components can potentially be manufactured with this technique in a simple and cost-effective way     

A WDM receiver photonic integrated circuit with net on-chip gain

We demonstrate a photonic circuit with an optical preamplifier, a WDM filter and a fast photodetector integrated on the same chip. The passive integrated filter is formed by an aspheric waveguide lens and a planar Bragg grating. This arrangements yields narrow filter response (8 Å width at -3 dB is demonstrated) and high rejection ratio of 24 dB. The optical preamplifier consisting of strained multi-quantum well layers provides sufficient amplification to overcome the passive losses. Response curves demonstrate net on-chip gain with low ripple     

Real-time in situ monitoring of antireflection coatings forsemiconductor laser amplifiers by ellipsometry

Very strict requirements need to be met for producing a high-quality single-layer antireflection coating on a traveling-wave laser amplifier facet. In order to obtain a facet reflectivity of 10^-4 or less, the index of refraction and the layer thickness of single-layer coatings have to be controlled to better than 0.03 and 30 Å, respectively. An innovative approach to highly controlled antireflection layer deposition based on in situ real-time ellipsometry is presented. Index control within ±0.01 and a facet reflectivity on the order of 10^-4 are reproducibly obtained