H. Horikawa

Polarization insensitive semiconductor laser amplifiers with tensile strained InGaAsP/InGaAsP multiple quantum well structure

Data on semiconductor laser amplifiers with a small tensile strain in the wells of multiple quantum well structures are presented. Semiconductor amplifiers with a small strain of 0.2% exhibit polarization insensitive characteristics with a signal gain of 15 dB in the 1.5 μm wavelength range. The enhancement of TM mode gain due to tensile strain is studied by measuring the dependence of amplified spontaneous emission spectra on device length and tensile strain.

Heteroepitaxial growth of InP on a GaAs substrate by low‐pressure metalorganic vapor phase epitaxy

Good quality InP was successfully grown on (100)GaAs 2° off normal toward [011] substrates by introducing low‐temperature grown GaAs/InP double buffer layers. It was found that addition of a thin GaAs buffer layer (20 nm thick) grown at low temperature (430 °C) between the GaAs substrate and an InP buffer layer was effective for improving the crystal quality. The full width at half‐maximum of the x‐ray rocking curve was as narrow as 200 arcsec for a 6‐μm‐thick InP layer. An electron mobility of 15 000 cm2/(V s) at 77 K was obtained for an unintentionally doped layer. The intensity of the photoluminescence at 77 K was as good as that for an InP substrate.

Low-drive-voltage MQW electroabsorption modulator for optical short-pulse generation

This paper reports on InGaAsP-InGaAsP tensile strained MQW electroabsorption (EA) modulators with a high modulation efficiency of 35 GHz/V that generate optical short pulses. We studied and optimized the multiple-quantum-well (MQW) structural parameters, barrier height, and well number, thickness, and strain in the absorption layer to ensure high attenuation efficiency and generate low duty cycle pulses. Low TE/TM polarization sensitivity was obtained by controlling strain. Stable, nearly transform-limited optical pulse trains with a narrow pulsewidth of 3.6 ps are generated by applying a 20-GHz sinusoidal modulation voltage (6 V/sub pp/) to the EA modulator. This achieves a very small pulse duty cycle of 7.2%.

Improved operation characteristics of long-wavelength lasers using strained MQW active layers

Long-wavelength semiconductor lasers and amplifiers with strained MQW structures as active layer materials in the region of 1.48-1.55 /spl mu/m are reported. Various improvements in device performance by employing the strained MQW structures were experimentally demonstrated in high-power operation at 1.48 /spl mu/m, high-speed operation with narrow linewidth at 1.55 /spl mu/m, and polarization-insensitive optical amplification in the 1.5 /spl mu/m band. A compressively strained InGaAsP/InGaAsP MQW structure was used for high-power operation. The maximum power could be increased by introducing a compressive strain into the well layers, as theoretically predicted. This increase can be attributed to the suppression of Auger nonradiative recombination and intravalence band absorption. High-speed characteristics were tested on two different active layer materials. The compressively strained InGaAsP/InGaAsP MQW structure proved to be better than the strained InGaAs/InGaAsP MQW structure as an active layer material because of its high differential gain at low threshold current due to a smaller valence band density of states and small carrier life time. Compressively strained InGaAs/AlGaInAs MQW structure, having larger quantum confinements due to larger band offsets than the InGaAsP-based structures, were employed for the high-speed laser. The relaxation frequency was estimated to be 26 GHz, and a small linewidth enhancement factor of 1.5 was obtained. Polarization insensitive optical amplification in the semiconductor laser amplifiers (SLAs) was demonstrated by using the tensile strained MQW structure. The device length and strain were optimized for polarization insensitive amplification. >

High‐power and high‐speed 1.3 μm V‐grooved inner‐stripe lasers with new semi‐insulating current confinement structures on p‐InP substrates

A significant improvement in the maximum output power of a 1.3 μm GaInAsP/InP laser with a semi‐insulating current confinement structure is reported. The improvement has been achieved by interposing an n‐type InP layer between a p‐InP substrate and an Fe‐doped InP layer. A maximum cw output power of 180 mW and a modulation bandwidth of 8.5 GHz have been obtained.

High‐power 1.48 μm multiple quantum well lasers with strained quaternary wells entirely grown by metalorganic vapor phase epitaxy

This letter describes 1.48 μm multiple quantum well (MQW) lasers with strained GaInAsP quaternary wells entirely grown by metalorgainic vapor phase epitaxy. The GaInAsP quaternary layers with 1.5% biaxially compressed strain showed an excellent crystal quality and an abrupt interface within half‐monolayer fluctuations which was verified with photoluminescence spectroscopy. The maximum continuous wave output power of 140 mW was obtained at 20 °C with 1500‐μm‐long lasers whose facets were coated by anti‐ and high‐reflection films. The small internal loss of 12 cm−1 and a high internal efficiency of 70% were obtained.

High‐power and high‐speed semi‐insulating blocked V‐grooved inner‐stripe lasers at 1.3 μm wavelength fabricated on p‐InP substrates

A maximum cw power of 90 mW at 25 °C was obtained for a GaInAsP/InP laser with a semi‐insulating InP current blocking layer grown by metalorganic vapor phase epitaxy on a p‐type InP substrate, a 700‐μm‐long cavity, and an antireflection coating on the front facet. The 3 dB bandwidth was in excess of 6 GHz with a low parasitic capacitance of 15 pF despite the long cavity. The semi‐insulating layer with the resistivity of 5×107 Ω cm was formed by doping only Fe. The current blocking characteristics of the blocking layer with the same configuration as the lasers were examined under various temperatures.

Hetero-epitaxial growth of InP on Si substrates by LP-MOVPE

Abstract A novel hetero-epitaxial technique for growing good quality InP layers on Si (100) 2° off normal toward [011] substrates has been developed. The key element of this process is introducing a thin GaAs buffer layer (10–20 nm) at a low temperature (430°C) followed by a thin InP buffer layer (10–20 nm) at low temperatures (400–550°C). The layers grown by this technique show a single domain structure, a narrow X-ray full width at half maximum (250 arc sec), a narrow spectral linewidth of photoluminescence at 77 K (10.5 meV) and a relatively low etch pit density ((1–2)×10 7 cm −2 ).

Strained layer quantum well semiconductor optical amplifiers : polarization insensitive amplification

Abstract : Optical amplifiers are important devices for future optical fiber transmission and other photonic technologies. Semiconductor laser amplifiers are attractive candidates for these applications because of theirs high gain, compactness, possibility of integration with light source and so on. In comparison with fiber amplifiers such as Er+-doped fibers, the semiconductor laser amplifiers have a disadvantage which is large difference between TE and TM gain. Therefore, to control the TE/TM mode gain is a key item in the development of semiconductor amplifiers. For polarization insensitive amplification in the semiconductor laser amplifier, several approaches have been proposed by geometric designing of active layers. 1-3 In this paper, we describe an approach to the polarization insensitive optical amplifier in which active layer consisted of GaInAsP multiple quantum well structures with biaxially tensile strains within well layers. A group has reported a strained layer quantum well amplifier with tensed barriers. 4 In this work, we investigated the effects of biaxially tensile strain on amplification in the quaternary strained quantum well amplifiers. The polarization insensitive amplification was successfully demonstrated.

High‐power InGaAs‐GaAs strained quantum well lasers with InGaP cladding layers on p‐type GaAs substrates

We report device results from channel guide InGaAs‐GaAs strained quantum well lasers with In0.49Ga0.51P cladding layers (λL = 980 nm). Channel guide lasers are demonstrated with a new current blocking scheme using a p‐n‐p InGaP junction on a p+‐GaAs substrate. The laser structure is grown by metalorganic vapor phase epitaxy on the channeled n‐InGaP layer. The reverse biased p‐n‐p InGaP junction is shown to be effective in preserving the current blocking properties for InGaAs‐GaAs‐InGaP lasers. The uncoated lasers show cw laser thresholds of 11 mA at RT and high output powers of 125 mW.