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The characteristics of gain-guided GaAs single-quantum-well laser arrays, using proton bombardment to confine the current flow to 11 stripes on 9-/spl mu/m centers, are described. The longitudinal-mode spectrum, the spectrally resolved far-field, and the near-field of this laser array were studied experimentally up to three times threshold current. The laser arrays are found to emit at /spl sim/10 longitudinal modes corresponding to the Fabry-Perot modes of the laser. The longitudinal spectrum is current dependent. Near threshold current, the spectrum consists of a number of longitudinal modes where only the fundamental mode of the array laser. At larger current, each of the longitudinal modes is broadened and the spectrum of each longitudinal mode consists of many individual emission lines of the array modes. For each longitudinal mode, the lowest order array mode emits at the longest wavelength and the highest order array mode emits at the shortest wavelength. The wavelength separation between neighboring array modes increases with increasing mode order. Fourteen array modes are found to emit simultaneously at three times threshold current. The experimental results are in good agreement with direct array-mode analysis based on the finite-difference method.

We have utilized a new aluminum source, trimethylamine alane (TMAA), in the growth of graded‐index separate‐confinement heterostructure single quantum‐well GaAs/AlGaAs laser structures by low pressure (30 Torr) organometallic vapor‐phase epitaxy. We find lower carbon and oxygen incorporation in AlGaAs epilayers using TMAA since it does not contain a direct Al–C bond and it is not susceptible to the formation of volatile Al–O containing compounds. The oxygen and carbon concentrations were below the detection limits (< 5 × 1016 cm−3 and < 3 × 1016 cm−3, respectively) of the secondary ion mass spectrometry measurements. Broad‐area lasers with 10‐nm quantum wells and Al0.45Ga0.55As cladding layers exhibited threshold current densities of 140 A cm−2 for cavity lengths of 1 mm, internal quantum efficiencies of 81%, and intrinsic losses of 1.6 cm−1. These results demonstrate that extremely high‐quality AlGaAs and GaAs quantum wells can be grown with TMAA.

The authors describe InGaAsP-InP index guides strip buried heterostructure lasers (SBH) operating at 1.3 mu m with a 1.1- mu m guiding layer grown by a two-step atmospheric pressure metalorganic chemical vapor deposition (MOCVD) growth procedure. These lasers are compared with buried heterostructure lasers having similar guiding layers under the active layer but terminated at the edge of the active layer. SBH lasers with 0.15- mu m-thick active layer strips, 5- mu m wide, and guide layers varying from 0 to 0.7 mu m have threshold currents increasing from 34 to 59 mA, and nearly constant differential external quantum efficiencies of 0.2 mW/mA. The threshold current increases more rapidly with temperature with increasing guide layer thickness, with T/sub 0/ decreasing from 70 degrees C for lasers without a guide layer to 54.3 degrees C for lasers without a guide layer to 54.3 degrees C for lasers with 0.7- mu m-thick guide layers. Output powers of up to 30 mW/facet have been obtained from 254- mu m-long lasers and were found to be insensitive to guide layer thickness. >

The vertical cavity surface emitting laser is of growing interest because of unique advantages offered by the device geometry, including the potential for the integration of this laser structure with other devices for OEICs. Additional advantages include the potential for ultra-small active volume devices, light emission normal to the wafer surface, and large-area two-dimensional arrays. In this paper we present data on various heterostructures grown by metalorganic chemical vapor deposition directed towards the realization of a high-efficiency VCSEL in the lattice-matched InP-In 0.47 Ga 0.53 As system.

Low‐frequency electrical current noise measurements are reported on double‐heterojunction AlGaAs/GaAs laser diodes fabricated on GaAs and on Si substrates. The noise spectra show a frequency dependence proportional with f−γ with γ close to unity. The spectral intensity is proportional to the current for smaller currents ( 1 mA). The diodes built on the GaAs substrate are 50 times less noisy than the ones built on the Si substrate. This effect is attributed to the fact that the density of dislocations at the Si interface is much larger than at the GaAs substrate/device interface.

The thermally induced biaxial stress in GaAs lasers grown on Si substrates is reduced by patterning the active region to an effective width of 10 μm and by introducing a compensating stress from a thermally deposited SiO2 layer. The largest stress compensation is obtained for oxide stripe lasers and results in a significant reduction in the degradation rate of the lasers.

Two-dimensional arrays of 3*3 vertical cavity surface emitting GaAs-AlGaAs lasers with 7- mu m center spacing are described. The lasers were grown by molecular beam epitaxy and contain one grown GaAs-AlAs mirror under the active layer and a second, thermally deposited, high-reflectivity, SiO/sub 2/-Si mirror on top of the epitaxial layer. The array has a 295-K threshold of 90 mA, corresponding to 10 mA per laser. The individual lasers in the array have Gaussian beam profiles both spatially in the near field and angularly in the far field. When all the lasers in the array are operating in a coupled manner, the emission exhibits a lobed far-field pattern with a 5 degrees separation in the direction parallel to the contact edge and a 2.5 degrees separation perpendicular to the contact edge. >

We describe the implementation of a scanning Hall probe microscope of outstanding magnetic field sensitivity (∼0.1 G) and unprecedented spatial resolution (∼0.35 μm) to detect surface magnetic fields at close proximity to a sample. Our microscope combines the advantages of a submicron Hall probe fabricated on a GaAs/Al0.3Ga0.7As heterostructure chip and the scanning tunneling microscopy technique for precise positioning. We demonstrate its usefulness by imaging individual vortices in high Tc La1.85Sr0.15CuO4 films and superconducting networks, and magnetic bubble domains.

We report the growth and fabrication of InGaAs/GaAs strained quantum well (QW) lasers with a very low threshold current density, Jth, of

The threshold current density, internal quantum efficiency, internal loss, and emission wavelength of InGaAsP/InP multiquantum well lasers, grown by atmospheric pressure metalorganic chemical vapor deposition, were measured as a function of substrate orientation on and away from the (001) towards the nearest [011] and [111]A. The laser parameters are optimized for (001) oriented substrates. Substrate misorientations of more than 3° in either direction yield lasers with increased threshold current density and lower internal quantum efficiency. The internal loss increases and the surface morphology becomes visually poorer for substrate misorientations of 6°. The laser emission shifts to longer wavelength with increasing misorientation.

Graded refractive index In0.2Ga0.8As/GaAs strained single quantum well ridge lasers, emitting at 0.98 μm, have been grown by molecular beam epitaxy. For pulsed excitation, laser operation has been obtained up to 180 °C for 1016‐μm‐long lasers. This record high operating temperature results from a high T0=160 °C characteristic of these long lasers. Anomalous threshold current dependences on temperature are found for shorter lasers and are attributed to band filling at high current densities and a shift of the emission from the n=1 quantum level to the n=2 level.

Optically pumped lasing has been observed up to 100 K in a Cd 0.2 Zn 0.8 Te ZnTe superlattice grown on a GaAs Si substrate. At 100 K, rapid degradation of the lasing signal is seen. This result is inferior to that previously reported for a similar structure grown on a GaAs bulk substrate, for which room-temperature lasing was seen with no degradation. X-ray rocking curve and morphology measurements suggest that the II–VI epilayer has limited ability to heal the extra defects that are present when a GaAs Si , rather than a bulk GaAs, substrate is used.

Data are presented demonstrating the optically coupled operation of a 3×3 two‐dimensional array of AlxGa1−xAs‐GaAs vertical‐cavity surface‐emitting lasers. Room‐temperature threshold current for the array is 90 mA, with the device geometry allowing for light emission from the epitaxial side of the device.

Data are presented demonstrating room‐temperature operation of AlxGa1−xAs‐GaAs vertical‐cavity surface‐emitting lasers grown on Si substrates. The device structures are grown using molecular beam epitaxy and a grown‐in quarter‐wave AlAs‐GaAs stack is used as the n‐side reflector and a nonalloyed Ag dot used as the p‐side reflector/contact. Pulsed threshold currents of ∼125 mA are obtained for a 15‐μm‐diam device.

Two dimensional 3x3 coupled arrays of GaAs/AlGaAs vertical cavity surface emitting lasers (VCSELs) with 7 pm center to center spacing are described [l]. The VCSELs emit normal to the epitaxial surface of the wafer and their compact size, simplicity of fabrication and low threshold per laser makes them ideal for the array geometry. Earlier VCSELs had larger spacings between lasers and were not coupled [WI. The lasers were grown by MBE and had the geometry shown in Fig. 1 with one grown quarter wave 23.5 GaAs/AlAs layer pair mirror under the 1 pm thick GaAs active layer and a thermally deposited high reflectivity four layer pair SiO2/Si mirror over the epitaxial layer. The top contact consisted of a 2 pm wide metal grid with a 3x3 array of 5x5 pm2 openings deposited using lift-off through the first Si02 layer of the mirror. Contact to the grid was made by a 400 pm2 Cr/Au pad. In this geometry the lasing regions are defined by the top mirror array. The current injected through the metal grid diffuses and spreads out under the mirrors resulting in a spatially dependent carrier density that exhibits a slightly lower carrier density under the center of the mirror. The lowest order transverse mode of a single laser is Gaussian and the spatially dependent refractive index due to the carrier density introduces a self focusing of the beam outside the laser cavity.

We show that if the active region of a quantum‐well (QW) laser is grown at a high temperature such that the sticking coefficients of group III species are less than unity, the emission wavelength λ and threshold current density Jth are sensitive to the spatial variations in substrate growth temperature Ts despite the time average flux variations of less than 1% across the surface of a rotating 7.5 cm diam substrate in our molecular‐beam epitaxy system. InGaAs strained QW lasers, in which the active region is grown at Ts < 580 °C at which In and Ga have unity sticking coefficients, have uniform Jth (212±4 A cm−2) and λ(989±1 nm) on a 5 cm diam substrate. These lasers were grown with In mounting. In contrast, GaAs QW lasers, which are grown at ∼700 °C with In mounting, have less uniform Jth (395±20 A cm−2) and λ(850±9 nm). This is the result of nonuniform substrate heating which is partly due to voids in the In back coating. This causes variations in GaAs growth rate because of the high temperature dependen...

Using proton bombarded stripe geometry lasers which emit intense optical pulses, we have measured the width of the optical beam in the plane of the junction as a function of time during the pulse. The width of the beam is qualitatively proportional to the change in the carrier density. The width increases during the quiescent period between pulses where the carrier density increases by current injection and decreases during the emission of the pulse. For one laser studied in considerable detail, the full width at half intensity decreases from 9 μm at the start of the pulse to 7.2 μm at the end of the pulse. The reduction in the width results from the self-focusing of the beam. It is due to an increase in the refractive index and the decrease in the gain distributions near the center of the stripe. The reduction in the beamwidth concentrates the mode to a region of sufficiently higher average gain to compensate for the reduction in spatial gain distribution. The self-focusing acts to reduce the damping of the relaxation oscillations, and thus enhances the effect of other nonlinearities such as saturable absorption in causing pulsations. The thermal induced refractive index distribution across the stripe is shown to play a crucial role in the gain instability caused by self-focusing.

Quaternary InAs 1-x-y Sb x P y ) and ternary InAs 1-x Sb x have been grown on InAs substrates using liquid phase epitaxy. The quaternary layers are lattice matched to InAs for y = 2.2x , and have bandgaps greater than InAs. The ternary layers have lower bandgaps than InAs, but have larger lattice constants. Reasonable quality growth has been obtained up to x = 0.15 where the luminescence peak is shifted to ∼4 from 3.1 μm and the lattice mismatch is ∼0.01. Optically pumped laser emission at 3.1 μm has been observed from 77 to 100 °K using an InAs active layer with InAs 1-x-y Sb x P y clading layers. Laser emission at 3.9 μm has been observed from 77 to 125 °K using a InAs 1-x Sb x active layer, with x\sim 0.13 , and InAs cladding layers. Laser emission from intermediate ternary compositions has also been observed.

The characteristics of phase-coupled laser arrays fabricated using Schottky barriers on the p-contact to confine the current flow to 5 or 10 stripes on 9 μm centers are described. The gain guided laser spots are very equally spaced, and in some cases do not coincide exactly with the position or number of conducting stripes. The self adjusting nature of the active region, together with the phase shift of π between the neighboring N laser spots results in extremely smooth far-field patterns consisting of 2 narrow, intense outer lobes, and N-2 much weaker interior lobes. The mode structure closely approximates the higher order modes observed in wide stripe laser. The separation and width of the outer lobes is defined by diffraction theory, and determined by the separation and number of lasing spots. Deviations from diffraction theory are found in some cases. The contributions to the far field were studied by examining the magnified image of the exit facet as a narrow slit was passed across the far field. The phase contributions present in the far field were studied by introducing a relative phase shift between the two symmetric halves of the far field. The relative phase change modifies the interference pattern of the magnified near-field image, causing a spatial shift of the imaged spots in the plane of the junction.

Intense visible emission in the red, green, and blue has been observed from infrared to visible multiphoton Y1−xErxF3 upconversion phosphors pumped with 1.5‐μm radiation from InGaAsP‐laser sources. With 0.01

It is shown that the well‐known damped relaxation oscillation resonance in the small signal equations for the dynamic photon and carrier densities becomes more highly damped when the photon density is axially inhomogeneous. An antireflective coating with R=0.02 on one laser facet reduced the resonance in the light output from a 1.3‐μm Vee‐groove laser yielding a flat response with a 3‐dB bandwidth of 5 GHz. We also show that the wavelength modulation or chirp, due to the carrier‐dependent contribution of the refractive index, is largely eliminated.

The degradation of single-quantum-well graded-refractive-index GaAs lasers and light-emitting diodes grown on silicon substrates by metallo-organic vapor deposition is studied. The mechanism resulting in degradation appears to be identical with that observed in GaAs devices on GaAs substrates. However, the devices degrade very rapidly, even under pulsed operation, owing to the presence of a very high density of non-radiative regions which results from the dislocations caused by the 4.1% lattice mismatch between the GaAs and the silicon substrate. Continuous operation has been obtained up to 160 K. At higher temperatures the dark regions quench the emission 3–5 μs after the start of a current pulse. This prevents the continuous operation at room temperature of these lasers. During operation the dark regions grow rapidly in size by non-radiative electron-hole recombination in the presence of the large tensile stress in the epilayer. We estimate that it will be necessary to reduce the defect density to less than about 10 4 cm −2 and to prevent the growth of defects in the active layer in order to achieve reliable operation of light-emitting devices.

The bandwidth characteristics of single and multimode optical fibers have been investigated with single and multilongitudinal mode laser sources operating at 0.8, 1.3, and 1.5 μm. It is shown that single-mode fiber with a cutoff wavelength of 1.3 μm can support 1 Gb/s transmission over at least 7.5 km with a 0.8-μm laser source.

The pulsations in the laser emission from several lasers have been studied as a function of temperature, cavity length, external mirror illumination, and effect of mirror etching. Selected DH lasers with 12‐μm‐wide stripes delineated by proton bombardment and 380‐μm‐long cavities were used. The modulation depth of the pulsations at 300 °K increases approximately linearly with current above a threshold value and becomes fully modulated at high output powers. At intermediate temperatures, the modulation exhibits a similar initial slope but is not complete at the highest measured output. At low temperatures, well‐developed pulsations are not observed; the modulation reaches a maximum at a low amplitude level and then decreases. The frequency dependence of the pulsations indicates that when the modulation level is increasing, the frequency f is relatively constant, and above the maximum moduation f 2 increases approximately linearly with output power. The dependence on cavity length was studied using a series...

Gaussian shaped picosecond pulses as short as 62 ps have been obtained from an array of 10 phase-coupled multiquantum well GaAs lasers. Combined dc and 75 ps long current pulses from a comb generator were used. Single pulses were obtained with an average power of 50 mW at a 960 MHz repetition rate which corresponds to a peak power of 0.8 W. These pulse widths are in good agreement with a theory of pulse formation based on the carrier and photon density equations with the gain expanded in a power series in time to yield Gaussian pulses.

Recent progress of GaAs-on-Si technology is reviewed and the importance of initial nucleation is emphasized. Growth initiation with a gallium prelayer at a suitable low temperature combined with migration enhanced epitaxy and in-situ thermal annealing may be able to give substantially improved material quality. During the initial growth, use of the minimum necessary As4:Ga flux ration is found to be critical. Patterned growth or post-growth patterning releases tensile stress only if the growth edges are free. GaAs-on-Si was almost completely relaxed from stress by post-growth patterning to 5 μm × 5 μm size patterns. Steps on the surface owing to substrate misorientation do not affect the two-dimensional electron gas (2DEG) transport properties in AlGaAs/GaAs selectively doped heterojunction transistor (SDHT) structures. For a sheet density of 1012 cm−2, a 2DEG mobility greater than 50 000 cm2 V−1 s−1 at 77 K was obtained on silicon substrates, which was found to be adequate for the fabrication of the state-of-the-art devices. For 1 μm-gate-length SDHTs, maximum transconductances of 220 and 365 mS mm−1 were measured at 300 K and 77 K, respectively. A minimum propagation delay time of 28 ps stage−1 was measured at 300 K for direct coupled field effect transistor logic (DCFL) ring oscillators with a power dissipation of 1.1 mW stage−1. The propagation delay time reduced to 17.6 ps stage−1 at 77 K. These results are comparable to the SDHT technology on GaAs substrates.

The photodetection capabilities of 1.3- mu m channel substrate lasers are studied. The diodes can be used either as lasers or detectors in single-mode-fiber half-duplex communication links. As a detector, a responsivity of 0.26 A/W is obtained by efficiently coupling the input radiation into the facet using a lensed single-mode fiber. The spectral bandwidth extends from 1.1 to 1.37 mu m. The dark current at room temperature is 200 nA at 1-V bias and due in part to current leakage through the Fe-doped InP blocking layer. As lasers, the diodes have a frequency response of 4 GHz, and as detectors, the 3-dB bandwidth is 600 MHz. >

The longitudinal mode spectrum of stripe geometry double heterostructure (DH) lasers exhibits a spectral broadening of ∼ 0.8 A when the laser emits pulsations. The broadening results from a chirp to longer wavelengths which occurs during the ∼ 0.4 ns long pulse. The chirp is due to an increase of the refractive index resulting from the reduction in the carrier concentration during the pulse. Both plasma and band to band interactions affect the index change with the latter mechanism giving the dominant contribution. A comparison of the wavelength shift obtained during the pulse with the current dependent shift of the longitudinal modes at currents well below threshold confirms that the change in carrier concentration is responsible for the chirp.

Highly single longitudinal mode operation of 1.3 μm InGaAsP/InP buried crescent lasers has been obtained using a 60-600 \mu m long external cavity defined by a spherical mirror. The intensity of the neighboring modes was suppressed by a factor of 1200 for dc excitation and by a factor of 800 for combined dc and 250 MHz current modulation.

Active and passive mode locking of strip buried heterostructure lasers is observed using an external cavity consisting of a lens and a mirror. Using the second‐harmonic‐generation method to obtain the second‐order autocorrelation function we obtain Gaussian pulses as short as 35.7 psec (FWHM) at a 1.9‐GHz repetition rate. The optical spectrum of the mode locked laser consists of longitudinal modes of the composite cavity spaced by ∼0.05 A, whose amplitudes are modulated by the 2.09‐A‐mode spacing of the laser itself, and contained under a Gaussian envelope of 9.5‐A FWHM. Additional very sharp structure (∼1.6‐psec FWHM) in the autocorrelation is shown to result from the presence of several laser mode groups.

The dispersion of the refractive index corresponding to the group velocity n*_{1} has been measured as a function of wavelength. It is obtained from the longitudinal mode spacing of GaAs buried heterostructure lasers at threshold. The dependence of n*_{1} on wavelength contains an approximately constant term due to the refractive index n 1 and a strongly dispersive component due to -\lambda (\partialn_{1}/ \partial\lambda) . For a given spectral bandwidth, the dispersion of n*_{1} causes a temporal broadening of a pulse as it passes through the medium. This dispersive effect is shown to contribute to the width of 0.65 ps long pulses obtained recently from mode locked semiconductor lasers. By reducing the length of the laser, the dispersive effect is reduced and it is suggested that pulses as short as 10-13s should be obtainable from such mode locked semiconductor lasers.

We report picosecond pulse generation in low threshold buried optical guide lasers using combined direct and microwave current excitation. The pulse widths were obtained as a function of direct current for several levels of RF excitation using lasers 125 and 380 μm long. The pulses have a Gaussian shape with full widths at half maximum intensity ranging from 19 to 57 ps. The pulse widths were obtained from the second harmonic autocorrelation. The experimental results are in reasonable agreement with the theory of short pulse formation in sinusoidally modulated lasers. The pulse width decreases with increasing dc and microwave current, and decreasing laser length. The shortest pulses were obtained with a 125μm long laser using 0.25 W RF at 1 GHz and 35 mA de bias. Multiple pulses are emitted at high dc excitation levels. Using the above laser at the indicated current levels the emission consists of a burst of ∼10 pulses which are separated by 30 ps, and has an approximately exponentially decaying amplitude. Saturable absorption was introduced in the lasers by degradation and results in shortening the pulses. A comparison is made of the pulse widths obtained for sinusoidal microwave current modulation and for pulsed excitation where the excitation is obtained from a step recovery diode. Reduced pulse widths are obtained for short current pulse excitation.

The characteristics of index-guided strip-buried heterostructure lasers are described. The lasers are grown by a two-step process, consisting of the initial 5-layer planar growth by MOCVD, and after etching to define the strip buried wave guide, recovery by Al 0.65 Ga 0.35 As using LPE. The devices are highly uniform, having 20 mA thresholds, quantum efficiencies of 0.65, and T 0 of 163°C. The TE polarized emission was in the lowest order transverse mode and consisted of ∼ 6 longitudinal modes. CW output powers of 50 mW per facet were obtained from lasers with reduced output reflectivity, and pulsed powers of 95 mW per facet from uncoated lasers have been obtained. The far-field angular widths were \sim 23\deg and \sim 50\deg in, and perpendicular to the junction plane, respectively. The total optical conversion efficiency of the coated laser emitting 50 mW CW was 41.5 percent.

A modified strip‐buried‐heterostructure (SBH) laser is described where the LPE growth process self‐aligns the current‐confining stripes with the active GaAs strips. With these lasers current thresholds have been reduced from ∼180 mA in previous SBH laser to ∼70 mA for active GaAs strips of 380×10×0.2 μm. Excellent linearity in light‐current characteristics and symmetry in laser output from both mirrors were obtained under both pulsed and cw operations. cw operation has been achieved at heat‐sink temperature as high as 115 °C. The current thresholds Ith have an exponential variation with temperature of the form Ith∝exp(T/T0) where T0 was 110 °K. Relaxation oscillation and self‐pulsation was not observed for lasers with clean transverse modes in pulsed response up to current injection levels as high as 4Ith.

Single longitudinal mode operation of cleaved‐coupled‐cavity lasers formed by recleaving of 1.5‐μm InGaAsP buried crescent lasers is investigated as a function of bias current, temperature, and modulation frequency. The two‐cavity lasers are made to operate in a stable single mode by adjusting the bias levels of the electrically isolated and optically coupled sections. The wavelength stability with temperature results in a change of only 0.48 A/°C over a range of 14 °C. Single mode operation is preserved under direct modulation at rates as high as 1 Gb/s. The reduction in linewidth and the absence of partition noise makes these lasers useful for optical transmission through highly dispersive single mode fibers.

Double heterostructures consisting of InAs0.91 Sb0.09 active layers with Al0.5 Ga0.5Sb cladding layers were grown by molecular beam epitaxy on GaSb substrates. Optically pumped laser emission at 3.9 μm was observed from 80 to 135 K with an exponentially dependent threshold with T0=17 K. At 80 K the threshold corresponds to an effective current of 4 kA/cm2. This value represents a significant reduction when compared with previous results. For a 1‐μm‐thick active layer the full angular width of the far field at the half intensity point normal to the junction is 40° and is in reasonable agreement with the width calculated from the guide and cladding refractive indices.

An integrated multilayer laser consisting of three double heterostructure GaAs laser diodes connected in series by reversed biased p+n+ tunnel junctions have been grown by molecular beam epitaxy. The lasers operate at currents comparable to single double heterostructure lasers but at approximately three times the single laser voltage.

Proton bombardment at 3×1015–1016‐cm−2 dosage level and 300 keV has been used to introduce a ∼4‐μm‐long nonradiative region at one of the mirror facets. The region acts as a saturable absorber and converts the initially temporally stable optical emission to a pulsating behavior with a repetition rate in the 0.5–3‐GHz range.

We have fabricated low‐threshold, high‐quantum‐efficiency, room‐temperature AlGaAs‐GaAs double‐heterojunction injection lasers from epitaxial structures grown by metalorganic chemical vapor deposition directly on Si substrates. These devices have broad‐area (125 μm×250 μm) pulsed threshold current densities as low as Jth =3.5 kA/cm2 at ∼23 °C. Ridge‐waveguide stripe‐geometry lasers (5 μm×250 μm) have pulsed threshold currents as low as 130 mA at ∼23 °C. These stripe‐geometry lasers have total external differential quantum efficiencies as high as ηext ∼70%, a value equal to the ηext measured for similar double‐heterostructure lasers grown on GaAs substrates. These are the lowest threshold currents and highest external quantum efficiencies yet reported for lasers grown on Si substrates.

Arrays of five InGaAsP buried‐cresent large‐optical‐cavity lasers operating at 1.3 μm are described. The monolithically integrated arrays have threshold as low as 60 mA, external quantum efficiencies η≊55%, and operate in the fundamental transverse mode up to 50 mW per facet at room temperature. Despite the very close center to center spacing of 8 μm, no electrical or optical interaction between lasers has been observed.

A diffraction‐coupled laser array has been actively mode locked in an external cavity to yield Gaussian pulses as short a 61‐ps full width at half‐maximum with a peak power of 1.1 W and an average power of 0.07 W. The array consists of 10 lasers, each 3 μm wide with 9‐μm center to center spacing. It emits with a stable double‐lobed far‐field pattern characteristic of the out‐of‐phase coupling between neighboring lasers. These arrays may be useful where high peak as well as high average optical powers are required.

Simple, self‐aligned phase‐coupled laser arrays consisting of ten 3‐μm‐wide stripes are described. The current flow was confined to the stripes by a Schottky barrier over the remainder of the laser chip. This process, applied to the AlGaAs graded‐index structures grown by metalorganic vapor phase epitaxy, produced arrays with threshold currents as low as 20 mA/stripe. The devices are capable of output powers of up to 1 W/facet and operate at temperatures as high as 100 °C with a stable far‐field pattern. In addition, novel information on the phase coupling in these gain‐guided arrays has been obtained.

An array of 16 individual addressable lasers with 50‐μm center spacing has been monolithically integrated on a GaAs chip and cw bonded to a Si submount and copper heat sink. The lasers have the loss stabilized buried heterostructure geometry with separate optical and carrier confinement. The advantages of this laser geometry for integration into arrays are described.

It is found experimentally that the linewidth of a grating loaded external cavity semiconductor laser is inversely proportional to the square of the linear dimension of the overall cavity. This observed behavior is consistent with the existing theories on the linewidth of a laser with an extended passive cavity. A slope of 6.5×105 Hz cm2 is obtained from least‐squares fitting the linewidth vs 1/(cavity length)2 curve at 1 mW of power. However, the linewidth reaches a lower limit when the cavity length is extended beyond a certain limit. This result suggests that additional phase noise term should be included in the calculation of linewidths of these extended cavity semiconductor lasers. We also report a value as small as 18 kHz mW in the linewidth vs 1/(power) curve.

We report the observation of bursts of transform‐limited 0.65‐psec pulses at 1‐GHz repetition rates by passive mode locking of a buried optical guide laser in an external cavity. The lasers contain a saturable absorber at the exit facet, specifically introduced by 600‐keV proton bombardment at a 3×1015‐ cm−2 dosage level.

Separate confinement heterostructure wafers grown by gas source molecular beam epitaxy have been used to prepare ridge waveguide lasers operating up to 50 °C. Laser threshold currents varied from 45 to 65 mA at room temperature and output powers up to 9 mW have been obtained with the external quantum efficiency of ∼36%. Gain profile measurements indicate excellent material uniformity. Frequency response flat to at least 2 GHz is consistent with the material free of interfacial traps or any capacitive shunt paths.

It is shown that the deep level (∼1.0 eV) luminescence observed in double‐heterostructure lasers originates from the E3 radiation damage trap (Ga vacancy) or a closely related vacancy‐donor complex in the n‐type GaAs substrate region rather than in the active region as had been reported previously.

The optical pulsations in the output of semiconductor lasers are accompanied by a time variation of the diode voltage. During the optical pulse the voltage decreases by ≈2.5 mV, corresponding to a decrease in carrier population. In the interval between pulses the voltage recovers exponentialy with a 1.3±0.2‐nsec time constant to its prepulse value as a result of carrier injection into the active region.

We attribute the single longitudinal mode operation of some Er‐doped 1.5‐μm InGaAsP lasers, observed here, to inhomogeneities in the active layer resulting from the Er. These results do not rule out the possibility of gain narrowing by the Er when Er is properly incorporated in the active layer.