Yuki Atsuji

Sub-milliampere threshold operation of butt-jointed built-in membrane DFB laser bonded on Si substrate

We fabricated GaInAsP/InP waveguide-integrated lateral-current-injection (LCI) membrane distributed feedback (DFB) lasers on a Si substrate by using benzocyclobutene (BCB) adhesive bonding for on-chip optical interconnection. The integration ofa butt-jointed built-in (BJB) GaInAsP passive waveguide was performed by organometallic vapor-phase epitaxy (OMVPE).By introducing a strongly index-coupled DFB structure with a 50-µm-long cavity, a threshold current of 230 µA was achieved for a stripe width of 0.8 µm under room-temperature continuous-wave (RT-CW) conditions. The maximum output power of 32 µW was obtained. The lasing wavelength and submode suppression ratio (SMSR) were 1534 nm and 28 dB, respectively, at a bias current of 1.2 mA.

Room-temperature continuous-wave operation of membrane distributed-reflector laser

In this paper, we report on the first ever demonstration of a continuous-wave operation of an injection-type membrane distributed-reflector (DR) laser at room temperature. A threshold current of 250 µA was obtained with a stripe width of 0.7 µm, a DFB region length of 30 µm, and a DBR region length of 90 µm. An external differential quantum efficiency of 11% with a light output ratio between the front and the rear of 6.7 was obtained at the front waveguide.

Room-temperature continuous-wave operation of GaInAsP/InP lateral-current-injection membrane laser bonded on Si substrate

We successfully demonstrated room-temperature continuous-wave (RT-CW) operation of a lateral-current-injection (LCI) GaInAsP/InP membrane Fabry–Perot laser by benzocyclobutene (BCB) adhesive bonding on a Si substrate for the first time. Our results include, for example, a threshold current of 2.5 mA and an external differential quantum efficiency of 22% per facet were obtained for a stripe width of 0.7 µm and a cavity length of 350 µm. From measurements of the differential quantum efficiency as a function of the cavity length, an internal quantum efficiency of 75% and a waveguide loss of 42 cm−1 were obtained.

Monolithic Integration of Membrane-Based Butt-Jointed Built-in DFB Lasers and p-i-n Photodiodes Bonded on Si Substrate

We demonstrate a monolithic integration of lateral-current-injection (LCI)-type membrane-based distributed-feedback (DFB) lasers and p-i-n-photodiodes (PDs) using a butt-jointed built-in (BJB) structure bonded on a Si substrate using benzocyclobutene. The BJB structure to be integrated to the membrane optical devices was prepared by organometallic vapor-phase epitaxy. A threshold current of 280 μA was obtained under a room-temperature continuous-wave condition by adopting a strongly index-coupled DFB laser with a surface grating structure and a λ/4-shift region. A low dark current of 0.8 nA was obtained with the p-i-n-PD at a bias voltage of -1 V, and its photocurrent property coincided with the light output property of the membrane DFB laser.

Energy Cost Analysis of Membrane Distributed-Reflector Lasers for On-Chip Optical Interconnects

The power consumption of lateral-current-injection semiconductor membrane distributed-reflector lasers with a λ/4 shift region has been theoretically evaluated, in terms of their ultralow-power-consumption and high-speed modulation operations. This paper contains an investigation into the optimal structure of the membrane laser in terms of its energy cost, for use in on-chip optical interconnections. The total power consumption was evaluated, taking Joule heating into account by assuming the device resistance. It was found that the large Joule heating effect present in shorter cavities limits a reduction of their power consumption. As a result, an energy cost of 63 fJ/bit can be obtained for 10 Gb/s data transmission, while maintaining the necessary power output required for a cavity length of 12 μm. We have provided a guide for designing microcavity lasers in terms of their Joule heating power.

GaInAsP/InP Lateral-Current-Injection Membrane DFB Laser Integrated with GaInAsP Waveguides on Si Substrate

A lateral-current-injection membrane DFB laser integrated with GaInAsP waveguides and a detector was fabricated by butt-joint regrowth technique. As a result, a threshold current of 700 μA under room-temperature CW condition was obtained.

Low-threshold-current operation of lateral current injection membrane distributed-feedback laser bonded on Si

Toward realization of an ultralow-power-consumption semiconductor light source for on-chip optical interconnection, we have been investigating the lateral current injection (LCI) membrane distributed feedback (DFB) laser. This time, we realized membrane DFB laser with 158 nm core thickness and demonstrated room-temperature continuous-wave (CW) operation with a threshold current of 390 μA for the cavity length of 360 μm and the stripe width of 0.2 μm, which is lowest value ever reported in a DFB lasers on a Si substrate.

Low-power and high-speed operation capabilities of semiconductor membrane lasers — Energy cost limited by Joule heat

The power consumption of a lateral current injection (LCI) type membrane distributed reflector (DR) laser under a high-speed direct modulation was theoretically investigated. As the results, we found that there is an optimal cavity length, which can be determined by the series resistance, to minimize the power consumption. For an example., an energy cost of 37 fJ/bit can be obtained at a modulation speed of 10 Gb/s for the cavity length of 17 μm when the grating coupling coefficient of 1800 cm-1 and the resistivity of p-InP cladding layer of 0.035 Ω·cm are used.

Low-threshold-current operation of membrane distributed-feedback laser with surface grating bonded on Si substrate

A lateral-current-injection (LCI) membrane distributed-feedback (DFB) laser with a surface grating structure (incorporating a slight step) emitting in the 1550 nm wavelength range was fabricated on a Si substrate by the adhesive bonding of benzocyclobutene. For a semiconductor membrane thickness of 158 nm and a surface grating depth of 30 nm, a threshold current of as low as 390 µA, with a corresponding threshold current density of 540 A/cm2, was obtained for a cavity length of 360 µm and a stripe width of 0.2 µm under a room-temperature continuous-wave (RT-CW) condition.

Integration of membrane-based DFB laser and PIN photodiode on Si substrate toward on-chip interconnection

Membrane DFB lasers and photodiodes were monolithically integrated on Si substrate. A threshold current of 280 μA was obtained. A photocurrent of 3 μA was obtained for the laser output of 3 μW.