Shingo Masui

510–515 nm InGaN-Based Green Laser Diodes on c-Plane GaN Substrate

We succeeded in developing InGaN-based green laser diodes (LDs) with a wavelength of 515 nm under continuous-wave (cw) operation by improving the growth condition of epitaxial layers and structures of LDs. The LD structures were grown on conventional c-plane free-standing GaN substrates by metal organic chemical vapor deposition (MOCVD). The threshold current and threshold voltage at 515 nm were 53 mA and 5.2 V, respectively. The lifetime of 510–513 nm LDs was estimated to be over 5000 h under cw operation with an optical output power of 5 mW at 25 °C.

365 nm Ultraviolet Laser Diodes Composed of Quaternary AlInGaN Alloy

Ultraviolet (UV) laser diodes (LDs), whose active layer were quaternary AlxInyGa1-x-yN single-quantum well structure, were grown on epitaxial lateral overgrown GaN substrates by a metalorganic chemical vapor deposition method. We investigated the lasing wavelength dependence of UV LDs on the threshold current density. As a result, we succeeded in fabricating 365 nm UV LDs which are useful for various industrial uses because their wavelength is similar to that of the i-line of high-pressure mercury vapor lamps. The threshold current and voltage of the 365 nm UV LD under continuous wave (cw) operation at 25°C were 50 mA and 4.8 V, respectively. The estimated lifetime of the 365 nm UV LDs was approximately 2000 h at an output power of 3 mW under cw operation at 30°C. The shortest lasing wavelength was achieved at 354.7 nm under pulse current injection at 25°C.

CW Operation of the First-Order AlInGaN 405 nm Distributed Feedback Laser Diodes

The first-order AlInGaN 405 nm distributed feed-back (DFB) laser diodes were grown on the free-standing GaN substrates by a metal organic chemical vapor deposition method. The first-order diffractive grating was formed into an n-type cladding layer. As a result, we succeeded in demonstrating the first-order AlInGaN based 405 nm DFB laser diodes under cw operation. The threshold current and the slope efficiency were 22 mA and 1.44 W/A under cw operation at 25 °C, respectively. The single longitudinal mode emission was maintained up to an output power of 60 mW. The fundamental transverse mode operation with a single longitudinal mode was observed in the temperature range from 15 to 85 °C at an output power of 20 mW.

1 W A1InGaN based green laser diodes

The AlInGaN based green laser diodes were grown on c face GaN substrates by a metal organic chemical vapor deposition method. As a result, we succeeded in demonstrating 1W 525 nm Green LDs. The optical output power, voltage and the wall-plug efficiency at the forward current of cw 1.5 A were 1.01 W, 4.76 V and 14.1% at 25°C, respectively. The lifetime was estimated to be over 15,000 h by the lifetime test which was carried out under the condition of a constant current of 1.5 A at 50°C for 1000 h.

Recent improvement in nitride lasers

We report our recent improvement of watt class blue and green GaN based LDs. These LDs were grown on c-face GaN substrates by metal organic chemical deposition. The laser chip was mounted on the heat sink by the junction down method in TO-ø9 mm package for the suppression of the thermal resistance. The optical output power of 455nm blue LDs was obtained above 4.7 W at injection current of 3A. The average lifetime was estimated to be over 30,000 hours at case temperature of 65 degree C under 3A. In green LDs, 1 watt class 532 nm green LDs as same wavelength as second harmonic generation (SHG) green laser was developed and the wall plug efficiency was 12.1 %. And the longer lasing wavelength was achieved to 537 nm.

First-Order AlInGaN 405 nm Distributed Feedback Laser Diodes by Current Injection

The first-oreder AlInGaN 405 nm distributed feed-back (DFB) laser diodes were grown on the c-face sapphire substrates by a metalorganic chemical vapor deposition method. The diffractive grating, which was shaped by 108 nm deep grating of an 85.7 nm period with a sidewall angle 89°, was formed into a p-type waveguiding layer. As a result, we succeeded in demonstrating the first-order AlInGaN based 405 nm DFB laser diodes by pulsed current injection. The threshold current and the peak lasing wavelength of the DFB laser diode were 190 mA and 403.7 nm under pulsed current operation at 25 °C, respectively. The lasing spectrum was kept the single longitudinal mode emission up to an output power of 30 mW.

Blue and green laser diodes for large laser display

Watt-class AlInGaN blue and green laser diodes (LDs) on c face GaN substrate are fabricated. The optical output powers of blue LDs and green LDs were 3.75 W and 1.01 W, and the wall plug efficiencies were 38.5% and 14.1%, respectively. The lifetimes were estimated to be over 30,000 and 15,000 hours at a case temperature of 50°C.

Characterization of AlInGaN-based 405nm distributed feedback laser diodes

The first-order AlInGaN 405 nm distributed feed-back (DFB) laser diodes were grown on the low dislocation freestanding GaN substrates by a metal organic chemical vapor deposition method. The first-order diffractive grating whose period was 80 nm was formed into an n-type cladding layer. The fine tooth shape grating was obtained by the EB lithography and the dry etching. No additional threading dislocation could be found at the regrowth interface. As a result, we succeeded in demonstrating the first-order AlInGaN based 405 nm DFB laser diodes under cw operation. The threshold current and the slope efficiency were 22 mA and 1.44 W/A under continuous wave operation at 25 °C, respectively. The single longitudinal mode emission was maintained up to an output power of 60 mW. The fundamental transverse mode operation with a single longitudinal mode was observed in the temperature range from 15 °C to 85 °C at an output power of 30 mW. The lifetime was estimated to be 4000 h by the lifetime test which was carried out under the condition of a constant output power of 30mW at 25 °C for 1000 h. The single longitudinal mode emission was maintained for the life tested DFB laser diodes.