Hikaru Kouta

Tetragonal vanadates YVO4 and GdVO4 – new efficient χ(3)-materials for Raman lasers

Abstract Efficient room temperature multiple Stokes and anti-Stokes picosecond generation in tetragonal YVO4 and GdVO4 host crystals for lasing trivalent lanthanides (Ln3+) has been observed for the first time. All measured stimulated Raman scattering (SRS) wavelengths in the visible and near infrared are identified and attributed to the SRS-active vibration modes of these vanadates.

Attaining 186-nm light generation in cooled ?-BaB 2 O 4 crystal

The transparency range of ??BaB2O4 (BBO) was expanded by means of cooling, and the resulting absorption coefficient at 193.4 nm was reduced to 0.29 cm-1 at 91 K from 1.39 cm-1 at 295 K.?Further, generation of light at 186.0 nm (the measurement limit in air) by type I sum-frequency generation (SFG) based on fundamental (744-nm) and third-harmonic (248-nm) light from a Ti:sapphire laser was confirmed for cooled BBO.?Calculations based on observed data for SFG wavelengths and phase-matching angles indicate a potential for cooled BBO to generate wavelengths as low as 181.7 nm.

Wavelength dependence of repetitive-pulse laser-induced damage threshold in beta-BaB2O4.

The dependence on wavelength of repetitive-pulse (10 Hz, 8-10 ns) laser-induced damage on beta barium metaborate (BBO) has been investigated. The thresholds of dielectric breakdown in bulk crystal have been found to be 0.3 GW/cm(2) at 266 nm, 0.9 GW/cm(2) at 355 nm, 2.3 GW/cm(2) at 532 nm, and 4.5 GW/cm(2) at 1064 nm. Results indicate two-photon absorption at 266 and 355 nm, which helps to produce an avalanche effect that causes breakdown at each of the four wavelengths tested. Neither the BBO refractive indices nor the absorption spectrum change until breakdown occurs.

20Gbps/ch optical interconnection between SERDES devices over distances from chip-to-chip to rack-to-rack

20-Gbps signal transmission of up to 100 m between two SERDES devices has been demonstrated using newly developed driver and receiver ICs tuned to the characteristics of VCSELs, photodiodes, and electrical transmission line with which they are used.

Overview and future prospects of the use of lasers for packaging by the microelectronics and photonics industry in Japan

This paper presents an overview and future prospects of the use of lasers for packaging by the microelectronics and photonics industry in Japan. Various kinds of lasers and material processing technologies have been developed and applied for manufacturing electronic and photonic devices to meet the strong demands for high-performance, lightweight, low energy-consumption mobile digital consumer electronics, broadband optical fiber communications, low-emission and fuel-efficient, easy-to-steer smart cars, etc. This paper emphasizes solid-state lasers as convenient and versatile light sources for packaging advanced compact devices with sensitive passive or active components having small feature sizes. Some of the representative material processing applications using solid-state lasers for electronic and photonic devices are, opaque and clear defects repairing of LCDs, trimming of functional modules, fine-tuning of optical characteristics of photonic devices, forming of various micro-vias for high-density interconnection circuits, laser patterning of amorphous solar-cells, and high-precision laser welding of electronic components such as optical modules, miniature relays and lithium ion batteries. The recent progress in high-power ultra-short pulse solid-state lasers seems to be rapidly increasing their processing capabilities such as for fine adjustment of optical filters, etc.

Development of Alicyclic Polymers for Multimode Waveguide Array and its Characteristics for Use in Optical Interconnection

We have carried out elemental research and development regarding optical transmission technology to establish the petaFLOPS - (1015 floating point number operations per second) class supercomputer. We describe our development of an alicyclic polymer, waveguide arrays formed with the polymer, and their characteristics for multimode optical data transmission. We have also developed high-density optoelectronic modules with a 4.5times4.5times0.5-mm low-temperature co-fired ceramic (LTCC) substrate that transmits 12 signals, and demonstrated a 10-Gbps/ch error-free transmission with the polymeric-waveguide array. We also showed a 20-Gbps/ch optical eye as a transmitter with a 1.1-mum range InGaAs vertical-cavity surface-emitting laser (VCSEL).

40-channel optical power level monitor with micro pyramid mirrors formed in planar lightwave circuit

Summary from only given. We have developed a compact and mass-production 40-channel power level monitor based on a planer lightwave circuit (PLC). We believe our method has the following advantages. The combination of directional coupler and gold micro pyramid mirror makes it possible to tap any amount and anywhere on PLC even between arrayed waveguides. Because this method basically consists of well-established PLC process, wire bonding process and flip-chip mounting process, it is suitable for mass production.

Optical Interconnection Technology for the Next Generation Supercomputers

This article describes the new optical interconnection technology which would be indispensable to realize high throughput supercomputer. To achieve 20 Gbps signal transmission between two LSIs of the supercomputer, we have developed every necessary component of optical interconnect system such as vertical-cavity surface-emitting laser (VCSEL), PIN-photodiodes (PD), electrical transmission line, driver IC and receiver IC. Each device is designed to optimize high speed signal characteristics of throughout transmission system. With these components total transmission system between two LSIs is developed and 20-Gbps 100 m signal transmission is successfully demonstrated. This transmission system is applicable to actual supercomputer.

A Double thick-polymer technology to realize low signal pad capacitance suitable for high-speed data transmission

A Pad-on-Stacked-Polymer (PASPO) technology, based on low cost packaging process, has been developed by utilizing 13-µm-thick double polymer layers and modified signal land design. The bottom photosensitive polymer shows higher via-hole resolution and higher chemical tolerance than conventional passivation polymer. The highly-reliable top polymer is planarized by CMP. For the 20-µm-square signal land, the PASPO technology drastically reduces the signal pad capacitance from 173 fF to 11 fF, and a clear eye opening for 40 Gbps signal transmission has been achieved for the low-k test chip.

Reliable refractive-index adjustment in Ge-doped silica-core planar waveguides by high-repetition rate femtosecond laser pulses

Laser trimming of phase errors are becoming vitally important technologies for silica-based planar waveguide devices such as arrayed-waveguide gratings (AWGs), directional couplers, etc. for Dense Wavelength Division Multiplexing (DWDM). Conventional phase trimming technologies based on UV excimer lasers have serious problems such as delicate and time consuming preparation for hydrogen-loaded sensitization processes, requirement of mask-processes and difficulty in real time, high-speed phase-error correction, etc. This paper presents some representative features of our novel technology for rapid and reliable refractive-index adjustment in germanosilica-based planar waveguides utilizing high-repetition rate ultrashort laser pulses. Infrared (800nm), 200 kHz, 150 fs pulses were used to increase refractive index of the planar waveguides with 100 µm/s scanning speed. With increase in the irradiation power density, maximum refractive-index increase up to ~2 × 10−3 was obtained with distinct saturation at around 2.2 TW/cm2. No decay in the refractive index change was observed even after annealing at 200°C for 100 hours. This highly stable refractive-index increase is in consistent with the phenomena of permanent refractive-index increase observed by Kondo, et al. in Ge-doped silica-core glass fibers irradiated by ultrashort laser pulses.Laser trimming of phase errors are becoming vitally important technologies for silica-based planar waveguide devices such as arrayed-waveguide gratings (AWGs), directional couplers, etc. for Dense Wavelength Division Multiplexing (DWDM). Conventional phase trimming technologies based on UV excimer lasers have serious problems such as delicate and time consuming preparation for hydrogen-loaded sensitization processes, requirement of mask-processes and difficulty in real time, high-speed phase-error correction, etc. This paper presents some representative features of our novel technology for rapid and reliable refractive-index adjustment in germanosilica-based planar waveguides utilizing high-repetition rate ultrashort laser pulses. Infrared (800nm), 200 kHz, 150 fs pulses were used to increase refractive index of the planar waveguides with 100 µm/s scanning speed. With increase in the irradiation power densi...