Μm InGaAsP Research Articles

1.3 μm InGaAsP Fabry-Perot lasers with reduced pulse jitter and power penalty

The pulse jitter and bit-error-rate performances of a 1.2 Gbit/s lightwave transmission system using 1.3 μm InGaAsP Fabry-Perot (FP) lasers with Zn-doped active layers were investigated experimentally. It was found that the pulse jitter and the resulting power penalty were strongly dependent on the carrier lifetime of the lasers. This suggests that dopedactive FP lasers with decreased carrier lifetime may be usable in a wider range of gigabit lightwave applications than previously considered.

Grafted InGaAsP light emitting diodes on glass channel waveguides

Optically pumped λ = 1.3 μm InGaAsP LEDs have been integrated with glass channel waveguides using epitaxial liftoff. Coupling of light from the grafted LEDs to the waveguides has been achieved with the aid of an overlayer film with tapered ends. Under pulsed operation, devices exhibit a laser-like threshold but without spectral narrowing.

Effects of nonlinear gain on four-wave mixing and asymmetric gain saturation in a semiconductor laser amplifier

Nearly degenerate four-wave mixing (NDFWM) and asymmetric gain saturation were studied in a 1.5 μm InGaAsP semiconductor laser amplifier at highly saturated conditions (Pout ≫ Psat) and frequency separations up to 500 GHz. Apart from modulation of the carrier density the data reveal a new mechanism of NDFWM with a characteristic time of about 650 fs which takes over when the frequency separation exceeds 100 GHz.

1.3 μm InGaAsP ridge waveguide laser on GaAs and silicon substrates by thin-film transfer

A new thin-film transfer technique has been developed that eliminates the handling of fragile, free-standing films. This, process was used to demonstrate the first long wavelength laser fabricated on a host substrate by a thin-film transfer technique. Ridge waveguide lasers operating at a wavelength of 1.3 mu m were fabricated on both GaAs and silicon substrates. The light-current characteristics of these transferred lasers were comparable to conventional lasers.< >

Determination of the gain nonlinearity time constant in 1.3 μm semiconductor lasers

By comparison of the measured K factors (ratio of the damping factor to the square of the resonance frequency) of distributed feedback and Fabry–Perot lasers, it is found that the relaxation time associated with nonlinear gain for 1.3 μm InGaAsP lasers is about 0.1 ps. This short time constant is consistent with spectral hole burning being the dominant process responsible for the nonlinear gain.

Effect of wafer cleavage on composition of InGaAsP grown on InP by low pressure MOCVD

The compositional uniformity of λ = 1.3 μm InGaAsP grown over 50 mm diameter substrates is severely degraded if the substrate is cleaved. The effect of cleaves either parallel or perpendicular to the direction of gas flow in the reactor has been observed. An increase in the phosphorus mole fraction of the quaternary alloy is noted near the cleave, and is attributed to an increase in the decomposition of the PH 3 precursor gas at the cleavage site. The decomposition products of PH 3 pyrolysis then re-enter the gas stream, making the cleave a PH 3 cracker during low pressure MOCVD crystal growth.

Broader spectral width InGaAsP stacked active layer superluminescent diodes

Fabrication and characteristics of broader spectral width 1.3 μm and 1.5 μm InGaAsP superluminescent diodes having a novel stacked active layer (STAC-SLDs) structure are reported. The emission spectral width is successfully broadened as much as twice that of conventional SLDs, yielding spectral widths of 80 and 140 nm for the 1.3 μm and the 1.5 μm SLD, respectively.

Simultaneous measurement of spontaneous emission rate, nonlinear gain coefficient, and carrier lifetime in semiconductor lasers using a parasitic-free optical modulation technique

An optical modulation technique is used to determine three important parameters for 1.3 μm InGaAsP diode lasers: the rate of spontaneous emission into the guided modes, the nonlinear gain coefficient, and the carrier lifetime at threshold. These results are unaffected by electrical parasitics, and are essential to understanding the noise and modulation properties of diode lasers.

Extremely high-frequency (24 GHz) InGaAsP diode lasers with excellent modulation efficiency

1.3 μm InGaAsP lasers with 3 dB bandwidths of 24 GHz and intrinsic resonance frequencies in excess of 22 GHz have been successfully fabricated. This is the highest bandwidth ever reported for a semiconductor laser, and the highest resonant frequency for InGaAsP lasers. Excellent modulation efficiencies are observed to high frequencies.

Experimental study of guided-wave modes in 1.3 μm InGaAsP light-emitting diodes

We report the results of an experimental study of the far-field characteristics of InGaAsP edge-emitting light-emitting diodes. Our results show that the asymmetric structure in the transverse far-field distribution of the device is caused by modes which are supported by the asymmetric dielectric waveguide. These modes propagate in the InP cladding layer with the higher refractive index at an angle to the fundamental mode. Their relative intensities, compared to the fundamental mode intensity, increase as the active layer thickness decreases below 0.1 μm, accounting for the observed concomitant decrease in the fiber-coupling efficiency of these devices.

Measurement of relaxation resonance, damping, and nonlinear gain coefficient from the sidebands in the field spectrum of a 1.3 μm InGaAsP distributed feedback laser

We calculate an expression for the fine structure in the field fluctuation spectrum of a semiconductor laser in terms of accessible device parameters. We measure the spectrum of an InGaAsP DFB laser and determine the linewidth, relaxation resonance, and damping versus current. From the relation between damping and current, we determine the nonlinear gain coefficient.

Observation of positive and negative nonlinear gain in an optical injection experiment: Proof of the cavity standing-wave-induced nonlinear gain theory in 1.3 μm wavelength semiconductor diode lasers

The origin of nonlinear gain in 1.3 μm InGaAsP semiconductor diode lasers is studied by measuring the magnitude and phase of a probe laser’s frequency response to optical injection with orthogonally polarized light from a pump laser. The sign and magnitude of the gain nonlinearity induced by optical injection depend on wavelength separation between pump and probe laser. The maximum magnitude of the nonlinear gain parameter is about 1.5×10−15 cm2. These results are consistent with the recently proposed theory that nonlinear gain is caused by the feedback from the dielectric grating induced by the standing wave in the laser cavity.

Efficient Er3+-doped optical fiber amplifier pumped by a 1.48 μm InGaAsP laser diode

Optical gain characteristics of an Er3+ -doped silica fiber have been studied by end pumping with a 1.48 μm InGaAsP high-power laser diode. A gain as high as 12.5 dB was obtained for an absorbed pump power of 16 mW with a 3-m-long fiber. By constructing an Er3+ fiber ring cavity with a 3 dB single-mode fiber coupler, we have obtained continuous wave laser oscillation at a wavelength of 1.553 μm.

1.3 μm InGaAsP buried crescent lasers with cobalt-doped semi-insulating current blocking layers grown by metalorganic chemical vapor deposition

Cobalt-doped semi-insulating InP layers grown by low-pressure metalorganic chemical vapor deposition (LPMOCVD) have been used for the first time as a current blocking layer for 1.3 μm InGaAsP buried crescent lasers. Lasers with this cobalt-doped InP blocking layer have cw threshold currents as low as 8 mA at room temperature. This is the lowest cw threshold current yet reported for an InGaAsP laser with a semi-insulating current blocking layer. In addition, the lasers exhibit total differential quantum efficiency of 60%, high-temperature operation up to 100 °C, high output power of 30 mW/facet, and a 3-dB modulation bandwidth of 11.6 GHz. These results indicate that the cobalt-doped semi-insulating InP layer grown by LPMOCVD provides effective current blocking for high-performance lasers.

Distortionless picosecond pulse amplification and gain compression in a traveling-wave InGaAsP optical amplifier

Pulses of 3–9 ps duration at wavelengths between 1.22 and 1.27 μm are amplified by a 1.3 μm InGaAsP traveling-wave optical amplifier. The gain decreases linearly with the output energy by up to 2.6 dB at the highest available energies. The output energy and peak power of the amplified pulses are as large as 4 pJ and 400 mW, respectively. It is shown that the gain compression can be described by treating the amplifier as a homogeneously broadened two-level system. No distortion of the pulse shape is observed after amplification.

Electro-optical effects of externally applied 〈100〉 uniaxial stress on InGaAsP 1.3 and 1.5 μm injection lasers

The changes in the polarization of the emission, spectrum, and light-current (L-I) behavior of a 1.3 and 1.5 μm InGaAsP channeled substrate buried heterostructure laser and double-channel planar buried heterostructure laser under an external uniaxial compressive stress perpendicular to the junction were studied at room temperature. It was found that the TM emission (electric vector perpendicular to the junction) reached threshold even at a stress level of ∼1×108 dyn cm−2. For stress ≤4×108 dyn cm−2, the TM emission, although reaching threshold first, was found to exist only over a limited range of currents. At high currents only TE emission (electric vector parallel to the junction) was observed. The appearance of the TE emission gave rise to nonlinear L-I characteristics. When both TM and TE emissions were seen, the former occurred at a higher energy. The limited stability of TM emission with current at low stresses is explained by invoking spectral hole burning effects which reduce the gain saturation power for TM mode than the TE mode. At high stresses ≥4×108 dyn cm−2, the increased gain for TM-polarized light ensures its stability at all currents. From our results it can be concluded that to avoid TM emission, and the associated spectral changes and nonlinear L-I characteristics, the tensile stress in the plane of the active layer should be less than 108 dyn cm−2.

FM noise and linewidth reduction in a 1.5 μm InGaAsP DFB laser coupled to an external fiber resonator

We report linewidth measurements on a 1.5 μm distributed-feedback semiconductor laser coupled to an external single-mode fiber resonator. The laser linewidth has been reduced from 100 MHz to 150 kHz by weak optical feedback from a 40 cm long fiber resonator having a finesse of 22. FM noise spectrum measurements demonstrate that high linewidth reduction with damped resonant noise peaks can be achieved by using high finesse external resonators.

Universal presence of saturable nonradiative currents in six types of 1.3 μm buried heterostructure lasers

Measurement of the carrier lifetime below threshold reveals that the saturable nonradiative current reported previously for 1.3 μm vapor-phase-regrowth buried heterostructure lasers is a widespread problem in 1.3 μm InGaAsP buried heterostructure lasers. The saturable nonradiative current represents 10%–30% of the threshold current for most geometries and about 6% for buried crescent lasers. This nonradiative current is also responsible for low spontaneous output at very low currents.

High-power operation of InP/InGaAsP double-channel planar buried-heterostructure lasers with asymmetric facet coatings

We report the high-power operation of λ=1.3 μm InGaAsP double-channel planar buried-heterostructure lasers with asymmetric mirror coatings. A stack of four dielectric layers is used to raise the reflectivity of one facet to over 80%, and the thickness of a single layer coating on the output facet is chosen to reduce the reflectivity to about 4%. The resulting lasers are characterized by a low threshold current of 25 mA, slope efficiency as high as 50%, and a power output of as much as 150 mW (at 5 °C) at a current of less than 300 mA. The lasers operate in a single transverse mode over the entire current range and as much as 45 mW of power could be coupled into a lensed single-mode fiber. Preliminary high-power aging data show excellent device reliability.

Frequency response of 1.3µm InGaAsP high speed semiconductor lasers

The frequency response of a group of 1.3 μm InGaAsP vapor-phase-regrown buried heterostructure lasers of various cavity lengths is analyzed by fitting the measured response curves. The dependence of resonant frequency f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> and damping rate <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\Gamma</tex> on bias power is determined. The differential gain coefficient for InGaAsP is determined as <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3.5 \times 10^{-16}</tex> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The damping rate is found to be proportional to the square of the resonant frequency with a proportionality factor which is independent of device geometry and facet reflectivity. The existence of such a universal relationship between <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\Gamma</tex> and f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> and the observed magnitude of the damping rate is explained by the interband relaxation model of nonlinear gain.