Akihiro Shima

A very narrow-beam AlGaAs laser with a thin tapered-thickness active layer (T 3 laser)

A very narrow-beam and high-power laser which has a thin tapered-thickness active layer is developed. The property of LPE on a ridged substrate is utilized to obtain the thin tapered-thickness active layer. In the T3laser, the active layer is thinner near the mirror than in the inner region. The main feature of the T3laser is the independent control of the beam divergence perpendicular to the junction ( \theta_{\perp} ) and the threshold current ( Ith ). That is, the narrow beam is obtained with little increase of Ith . Thus \theta_{\perp} as narrow as 10° has been obtained with Ith about 60 mA. The large near-field spot size of the laser is also suitable for high-power operation. The maximum output power of 120 mW in the fundamental transverse mode has been realized for a laser emitting at 780 nm. Stable 30 mW operation at 50°C has been confirmed over 7000 h.

A 67% PAE, 100 W GaN power amplifier with on-chip harmonic tuning circuits for C-band space applications

This paper describes a high efficiency and high output power GaN power amplifier for C-band space applications. The amplifier uses on-chip harmonic tuned FETs to improve dc-to-rf conversion efficiency. A 2nd harmonic input tuning circuit is incorporated into each unit on-chip FET cell and realizes high precise control of 2nd harmonic input impedance. In addition, 2nd and 3rd harmonic output impedances are optimized with external output matching circuits. A 100 W power amplifier with 4-chips achieves a 67.0% PAE (72.4% drain efficiency) at 3.7 GHz under CW operating conditions. To the best of our knowledge, this is the highest efficiency of C-band power amplifiers ever reported with over 100 W output power.

Uniform Fabrication of Highly Reliable, 50-60 mW-Class, 685 nm, Window-Mirror Lasers for Optical Data Storage

Uniform fabrication of highly reliable 50–60 mW-class 685 nm laser diodes (LDs) with a window-mirror structure has been realized by using selective solid-phase Zn diffusion and three-inch full wafer processing. A window-mirror structure at the LD mirror is formed by Zn-induced disordering of an ordered GaInP multiple quantum-well (MQW) active layer. High uniformity of characteristics such as the operating current and the far-field pattern has been obtained by realization of highly uniform Zn diffusion. A small astigmatic distance (ΔZ3 µ m), a low relative intensity noise (RIN-135 dB/Hz) and a high speed response (T r, T f1.2 ns) are obtained in addition to the high-power and high-temperature characteristics (70 mW, 80° C) in spite of the existence of the window structure. The LDs have exhibited reliable 6,000–10,000 h operation under the conditions of 60° C and 50–60 mW for the first time.

Highly Reliable 637-639 nm Red High-Power LDs for Displays

Higher power laser diodes (LDs) with a wavelength of 637-639nm are strongly demanded as a light source of display applications because luminosity factor of laser light is relatively high. In order to realize reliable high power operation, we have optimized LD structure, focusing on improvement of power saturation and sudden degradation. As a result, 40μm-wide broad-area (BA) LDs with window-mirror structure have been designed. We fabricated two kinds of single emitter LDs of 1.0mm cavity and 1.5mm cavity. The single LD is installed in conventional φ5.6 mm TO-CAN package. The 1.0mm LD showed very high wall plug efficiency (WPE) of 33% at 25 ºC (23% at 45 ºC) in the power range of around 300mW (30 lm). High output power of 600mW (60 lm) is realized by the 1.5mm LD. Both LDs have operated for over 1,000 hours without any degradation. Estimated mean time to failure (MTTF) is 10,000 hours. In addition, we fabricated an array LD consisting of 20 emitters (BA-LD structure), which shows reliable CW operation of 8W (at junction temperature of 50 ºC) for 10,000 hours.

A 780 nm high-power and highly reliable laser diode with a long cavity and a thin tapered-thickness active layer

Conventional AlGaAs laser diodes with uniform thickness active layers of various cavity lengths are investigated. It is recognized that the extension of the cavity length is effective in the improvement of the maximum output power, the temperature characteristics, and the operating life in high-temperature conditions. A 780-nm, high-power laser diode having a 350- mu m-long cavity with a thin tapered-thickness active layer was fabricated. The optical power density near the mirror facets, the thermal resistance, the current density, and the carrier density were reduced by this structure. The laser emitted over 100 mW of CW (continuous-wave) output power at temperatures up to 80 degrees C. A maximum output power level of 160 mW was achieved at room temperature. The fundamental transverse mode was confirmed at least up to 120 mW. >

640-nm laser diode for small laser display

Short wavelength and highly efficient AlGaInP quantum-well laser diode is promising as a red light source for small laser display application. Two kinds of the laser diodes are presented in this paper. A narrow ridge laser diode was designed for single lateral mode. In addition, a broad area laser diode was optimized for the higher power operation. To suppress a carrier leakage from an active layer, AlInP cladding layers were adopted to both of the lasers. Evaluation tests of the fabricated lasers were performed under CW operation. The wavelength of the narrow ridge laser was 636.0 nm under the condition of 25°C and 100 mW. Single lateral mode oscillation and the high wall plug efficiency of 29% were obtained. The beam divergences were 16° and 8° in fast and slow axes, respectively. The broad area laser showed lasing wavelength of 636.9 nm at 25°C for 200 mW output. The wall plug efficiency was 30% under this condition. Both of the lasers showed both high luminance and high wall plug efficiency. These lasers are suitable for small laser display applications.

Over 200-mW operation of single-lateral mode 780-nm laser diodes with window-mirror structure

The high-power operation of the lateral mode stabilized 780-nm AlGaAs laser diode (LD) with the window-mirror structure has been achieved. The stable lateral mode operation up to 250 mW is realized. This is the highest power record among the narrow stripe LDs with the wavelength of 780 nm. This LD is suitable for the next generation high-speed (16-24/spl times/) CD-R/RW drives needing 200 mW class LDs.

40G RZ-DQPSK transmitter monolithically integrated with tunable DFB laser array and Mach-Zehnder modulators

A 40G RZ-DQPSK transmitter monolithically integrated with a tunable DFB laser array and Mach-Zehnder modulators was developed for the first time. The optical waveform of 40Gb/s DQPSK was successfully demonstrated.

Multi-wafer growth of highly uniform and high-quality AlGaInP/GaInP structure using high-speed rotating disk metalorganic chemical vapor deposition

Multi-wafer growth of highly uniform and high-quality AlGaInP/GaInP using a high-speed rotating disk metalorganic chemical vapor deposition (MOCVD) has been successfully realized by suppressing In desorption and oxygen contamination at high growth temperature around 700°C. The suppression of In desorption during high-temperature growth is achieved by an increase of the effective gas flow rate resulting from increasing disk rotational speed and reducing growth pressure. The layer thickness uniformity of both undoped GaInP and Zn-doped (Al 0.7 Ga 0.3 ) 0.5 In 0.5 P layers is controlled within ± 5% over a 3-inch diameter wafer. The composition uniformity of undoped GaInP layer estimated form X-ray rocking curve is controlled within ± 2% over the 3-inch diameter wafer. The oxygen concentration in the (Al 0.7 Ga 0.3 ) 0.5 In 0.5 P layers is substantially reduced to below 2 × 10 16 cm −3 . Excellent performance, uniformity and reliability of AlGaInP/GaInP double quantum well laser diodes are also obtained from the 3-inch diameter wafer prepared by multi-wafer growth

Hign-Power Long-Cavity T3 Laser with a Very Narrow Beam

A 790 nm AlGaAs laser with a thin tapered thickness active layer (T3 laser), whose cavity length is 350 µm, has been developed. As the beam divergence of the laser becomes narrower, the threshold current does not increase. Both the current density and the thermal resistance can be reduced by extending the cavity length of the laser. The laser emitted a light output power over 100 mW even at 80°C and proved to have a fundamental transverse mode at least up to 120 mW. The stable 50 mW operation at 50°C over 2000 hours has been confirmed.