B. Borchert

1.55 mu m gain-coupled quantum-well distributed feedback lasers with high single-mode yield and narrow linewidth

The fabrication and characteristics of gain-coupled 1.55- mu m GaInAlAs quantum-well metal-clad ridge-waveguide distributed-feedback lasers are discussed. The gain-coupling mechanism was provided by a thin ternary loss grating layer with an estimated gain-coupling strength of about 30/cm. For as-cleaved devices, the single-mode yield was as high as 70 and 95% for 600- and 800- mu m-long devices, respectively. Typical threshold currents were 40 and 55 mA, respectively. Both the high single-mode yield and the pronounced asymmetric spectra were calculated theoretically and give a strong indication that a significant amount of gain coupling was realized in the laser structure. For a 600- mu m-long device, a continuous-wave (CW) output power of 10 mW and a minimum linewidth of 1.6 MHz were measured.<<ETX>>

Advanced 1.55 µm Quantum-Well GaInAlAs Laser Diodes with Enhanced Performance

The fabrication and characteristics of advanced 1.55 µ m quantum-well GaInAlAs laser diodes are presented. The strained layer laser structures were grown by metal organic vapor phase (MOVPE). By employing InP-cladding layers and an etch-stop layer, ridge-waveguide lasers with different longitudinal resonator types were processed by conventional chip technology. The following characteristics have been obtained, which mostly represent best values for 1.55 µ m GaInAlAs laser diodes: for Fabry-Perot (FP) lasers, cw operation at 130°C and a characteristic temperature of 95 K were observed; maximum output power was 46 mW; and the 3 dB bandwidth as high as 17 GHz. Gain-coupled distributed feedback (DFB) lasers with an absorptive grating show a single-mode yield about 75%, their 3 dB bandwidth being 11 GHz. Two-section gain-coupled DFB devices were continuously tunable over 3 nm. For negatively detuned index-coupled DFB devices an ultrahigh 3 dB bandwidth of 18.5 GHz was measured. All these characteristics are comparable to those of 1.55 µ m InGaAsP ridge-waveguide lasers. We report for the first time, the broad-area folded-cavity surface-emitting lasers using GaInAlAs which exhibit a threshold current density of 2 kA/cm2.

1.57 mu m strained-layer quantum-well GaInAlAs ridge-waveguide laser diodes with high temperature (130 degrees C) and ultrahigh-speed (17 GHz) performance

The fabrication of GaInAlAs strained-layer (SL) multiple-quantum-well (MQW) ridge-waveguide (RW) laser diodes emitting at 1.57 mu m is discussed. Due to an optimized layer structure, a very high characteristic temperature of 90 K was obtained. As a consequence for episide-up mounted devices, the maximum continuous wave (CW)-operation temperature is 130 degrees C. At room temperature, a maximum output power of 47 mW was measured for 600- mu m-long lasers with one high-reflection coated facet. The low series resistance of 4 Omega (2 Omega ) for 200- mu m-(400- mu m)-long devices yields an ultrahigh 3-dB bandwidth of 17 GHz. These static and dynamic properties also result from a high internal quantum-efficiency of 0.83 and a high differential gain of 5.5*10/sup -15/ cm/sup 2/.<<ETX>>

Optical network analysis and longitudinal structure characterization of fiber Bragg grating

A method for polarization-resolved optical fiber Bragg grating (FBG) characterization is reported on. The complete reflectance Jones matrix is measured interferometrically. Required polarization transformers need not be accurate, just to operate reproducibly, because redundant measurements yield pairs of orthogonal polarizations. Local dichroic reflectivity and birefringence of a sampled grating was derived from this data. Knowledge of these quantities should allow improvement of the ultraviolet (UV) illumination process and to effectively correct phase mask errors by longitudinally selective UV light postprocessing.

Asymmetric quantum wells with enhanced QCSE: modulation behaviour and application for integrated laser/modulator

We have optimized asymmetric InGaAsP QWs with respect to the quantum confined Stark effect (QCSE). We have found structures with a red shift of 40 meV at a field of 70 kV/cm. Moreover, it was our aim to find structures with a strong blue shift. A new principle for the integration of a laser and a modulator is presented, which is based on the application of blue shift asymmetric QWs in the active layer for laser and modulator simultaneously. A calculation of the laser and modulation properties for a QW-structure with 27 meV blue shift at a field variation of 70 kV/cm is presented.

Improved behavior of monolithically integrated laser/modulator by modified identical active layer structure

For the monolithic integration of laser and modulator an identical active layer structure is proposed. The combination of different multiquantum wells (MQWs) allows the reduction of the wavelength dependence of the absorption efficiency and the chirp. First experimental results are reported. Structures with two different MQW types and only one MQW type are compared.

Tunable twin-guide lasers with flat frequency modulation response by quantum confined Stark effect

For the first time results on the frequency modulation response of tunable twin‐guide laser diodes utilizing the quantum confined Stark effect in a multiquantum well modulation layer are presented. The structures were grown by metalorganic vapor phase epitaxy and were processed into ridge‐waveguide lasers emitting at 1555 nm. Preliminary devices exhibit single‐mode output power levels of more than 10 mW and minimum linewidths around 4 MHz. The frequency modulation response is flat up to 2 GHz with a modulation efficiency of 7 GHz/V.

High power quantum-well gain-coupled (GC) DFB lasers at 1.3 /spl mu/m and 1.55 /spl mu/m

Summary form only given. High power characteristics of InGaAsP quantum-well gain-coupled DFB lasers with a loss grating are presented. Among these are record single-mode (SM) values of 115 mW at 1.3 /spl mu/m and 95 mW at 1.55 /spl mu/m. The SM-yield at 20 mW is as high as 66%.

Linewidth broadening by 1/f noise in wavelength-tunable laser diodes

The excess linewidth broadening of continuously tunable InGaAsP/InP laser diodes at 1.5 μm wavelength is investigated. Terminal electrical and FM noise measurements indicate that the recombination processes in the forward biased tuning region produce significant 1/f carrier noise. Below 1 MHz the 1/f noise dominates yielding a noise enhancement of about 30 dB at 1 kHz. The discrepancy observed so far between theoretically expected and measured spectral linewidth can be well resolved by taking into account this additional noise source.

Tunable twin-guide lasers with improved performance fabricated by metal-organic vapor phase epitaxy

Tunable twin-guide (TTG) laser diodes have been fabricated using metal-organic vapor phase epitaxy (MOVPE) exclusively for all epitaxy stages. A significant performance improvement over previous experiments has been achieved with an effective current confinement in a considerably simpler laser structure. As a consequence, continuous wavelength tuning over 4.7 nm is obtained while maintaining a light output power per facet of 3 mW.<<ETX>>