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Rieko SATO Yasuhiro SUZUKI Naoto YOSHIMOTO Ikuo OGAWA Toshikazu HASHIMOTO Toshio ITO Akio SUGITA Yuichi TOHMORI Hiromu TOBA
A 1.55-µm hybrid integrated wavelength-converter module was fabricated using a two-channel spot-size converter integrated semiconductor optical amplifier (SS-SOA) on a planar-lightwave-circuit (PLC) platform. Clear eye opening and penalty-free wavelength conversion were obtained at 2.5-Gb/s modulation with a wide wavelength difference of 46 nm. The module showed good characteristics including low insertion loss (0.1 dB), and high conversion efficiency (-0.2 dB). It also showed stable wavelength conversion for as wide as a 13 temperature range.
Rieko SATO Yasuhiro SUZUKI Naoto YOSHIMOTO Ikuo OGAWA Toshikazu HASHIMOTO Toshio ITO Akio SUGITA Yuichi TOHMORI Hiromu TOBA
A 1.55-µm hybrid integrated wavelength-converter module was fabricated using a two-channel spot-size converter integrated semiconductor optical amplifier (SS-SOA) on a planar-lightwave-circuit (PLC) platform. Clear eye opening and penalty-free wavelength conversion were obtained at 2.5-Gb/s modulation with a wide wavelength difference of 46 nm. The module showed good characteristics including low insertion loss (0.1 dB), and high conversion efficiency (-0.2 dB). It also showed stable wavelength conversion for as wide as a 13 temperature range.
Yuichi TOHMORI Hiroyuki ISHII Hiromi OOHASHI Yuzo YOSHIKUNI
This paper describes the recent progress made in developing wavelength tunable semiconductor light sources for WDM applications. Wide and quasi-continuous wavelength tunings were investigated for a wavelength-selectable laser and a wavelength tunable distributed Bragg reflector (DBR) laser having a super structure grating (SSG). A wavelength-selectable laser consisting of a DFB laser array, a multi-mode interferometer (MMI), and a semiconductor optical amplifier (SOA) demonstrated a quasi-continuous tuning range of 46.9 nm by using temperature control. A wavelength-tunable DBR laser with SSG exhibited a quasi-continuous tuning range of 62.4 nm by using three tuning current controls. Wavelength stabilization was also demonstrated under the temperature variations of 5.
Hiroyuki ISHII Yuichi TOHMORI Fumiyoshi KANO Yuzo YOSHIKUNI Yasuhiro KONDO
This paper reports on broad-range wavelength tuning characteristics of DBR lasers which make use of a newly proposed multiple-phase-shift super structure grating (SSG). The reflection characteristics of the SSG reflector are analyzed theoretically. We found that the SSG reflector has periodic sharp reflection peaks each with high reflectivities thus making it a suitable wavelength selective reflector for single-mode lasers. The expected characteristics were evident in multiple-phase-shift SSGs fabricated using a new method which involves multiple-phase-shift insertion. DBR lasers with multiple-phase-shift SSGs were fabricated and their wavelength tuning characteristics were studied. The maximum tuning range is 105 nm in the single longitudinal mode under a CW condition. Dynamic single mode operation was also observed throughout the tuning range.
Yuichi TOHMORI Kazuhiro KOMORI Shigehisa ARAI Yasuharu SUEMATSU
Bundle-integrated-guide (BIG) structure distributed-Bragg-reflector (DBR) lasers based on 1.5-1.6 µm GaInAsP/InP system are presented. The significance of this structure is the suitability for the planar fabrication process of integrated optical devices, such as DBR lasers, which comprise active and passive waveguide regions. The BIG structure enables easier fabrication of buried hetero-structure (BH) of such an integrated waveguide device. High coupling efficiency between those waveguides of 95-99 percent is theoretically available with sufficiently large tolerance in thickness and composition of waveguide layers. Devices with different lengths of the active region, such as 200 µm, 100 µm and 50 µm, were fabricated and tested both for DC operation and rapid direct modulation. Threshold current as low as 28 mA and output power of 6.5 mW/facet were obtained for BH-BIG-DBR lasers with 100 µm long and 3 µm wide active region. Side-mode suppression ratio (SMSR) of more than 32 dB was obtained at the bias current of 1.2 times the threshold and it was not much degraded by rapid direct modulation.
Kazuhiro KOMORI Yuichi TOHMORI Shigehisa ARAI Yasuharu SUEMATSU
A dynamic-single-mode bundle-integrated-guide distributed-bragg-reflector (BIG-DBR-DSM) laser with short active region was experimentally demonstrated for low threshold current and high sub-mode suppression. CW threshold current of 22 mA was obtained for the case of active region length of 50 µm. Sub-modes were suppressed more than 35 dB.
Takuya TANAKA Hiroshi TAKAHASHI Yoshinori HIBINO Toshikazu HASHIMOTO Akira HIMENO Yasufumi YAMADA Yuichi TOHMORI
We describe the fabrication method and characteristics of hybrid external cavity lasers composed of a spot-size converter integrated LD (SS-LD) and a UV written Bragg grating in a planar lightwave circuit (PLC) on a Si substrate. The SS-LD is passively aligned on a Si platform formed in the PLC, and the UV grating is created in the PLC with ArF laser irradiation through a phase mask. This structure enables us to fabricate a stable single-mode laser with a precisely controllable oscillation wavelength. By using the above techniques, we obtained a threshold current of 7-8 mA and a side mode suppression of 37 dB for an external cavity laser operating at 1.3 µm. Moreover, we successfully demonstrated a four-channel external cavity laser with a wavelength interval of 2 nm 0.1 nm by integrating 4 SS-LDs on a PLC and controlling the Bragg wavelengths with ArF laser irradiation without a phase mask.
Yoshio ITAYA Yuichi TOHMORI Hiroshi OKAMOTO Osamu MITOMI Masato WADA Kenji KAWANO Hideki FUKANO Kiyoyuki YOKOYAMA Yasumasa SUZAKI Minoru OKAMOTO Yasuhiro KONDO Isamu KOTAKA Mitsuo YAMAMOTO Masaki KOHTOKU Yoshiaki KADOTA Kenji KISHI Yoshihisa SAKAI Hiromi OOHASHI Masashi NAKAO
We studied three types of lasers emitting narrow beam divergence of output light: 1) a spot-size converter integrated laser diodes (SS-LDs) with a vertically tapered waveguide, 2) one with a laterally tapered waveguide, and 3) one consisting of a small cross section of active region. We compared them with regard to their performance in coupling efficiency to a cleaved single mode fiber, threshold current, output power, and reliability. Both the spot-size converted integrated lasers with vertically and laterally tapered waveguide repeatedly provided low threshold currents of as low as 6 mA and low coupling loss to the fiber of 1.2 to 2.5 dB in two inch wafer processes. As a result of the aging test, the SS-lasers were predicted to have the same degradation rate as a conventional buried heterostructure laser. The laser having a small cross section of active layer also has low coupling loss and high efficiency up to 85.
Hiroshi FUKUI Yasuharu SUEMATSU Kazuhito FURUYA Yuichi TOHMORI Sigehisa ARAI
It was shown experimentally that the noise, which is estimated to be due to mode hopping among modes composed of a laser mirror and an external reflection point, was suppressed in distributed-Bragg-reflector(DBR) single mode lasers biased above a certain level. This tendency agree with our theoretical prediction.
Yasuyuki MIYAMOTO Chiaki WATANABE Masashi NAGASHIMA Kazuhito FURUYA Yasuharu SUEMATSU Yuichi TOHMORI Shigehisa ARAI
Fabrication of 1.5 µm GaInAsP/InP laser by OMVPE on p-type substrate is reported. Low threshold current density (1.2 kA/cm2) was obtained by reduction of growth time in order to prevent Zn diffusion from substrate. CW operations at room temperature were obtained in buried heterostructure (BH) devices fabricated by OMVPE-LPE hybrid growth method. No degradation was observed after 2000 hours' aging test.
Toshio ITO Katsuaki MAGARI Yasuo SHIBATA Yoshihiro KAWAGUCHI Yasuhiro KONDO Yuichi TOHMORI Yasuhiro SUZUKI
We propose a novel method of precisely measuring the polarization dependence of single pass gain (PDG) in a semiconductor optical amplifier integrated with spot-size convertors (SS-SOA). By averaging the signal gain of a SS-SOA over a wide wavelength range using the amplified spontaneous emission (ASE) of an erbium doped fiber (EDF), the PDG can be accurately estimated. This is because the influence of gain ripples on the measurement results are drastically reduced. We successfully evaluated the PDG of an angled-facet SS-SOA, even before the process of anti-reflection coating, within a small error of 0.5dB. The EDF-ASE technique is useful in sampling tests and selecting angled-facet SS-SOA chips from wafers. The polarization dependence of the coupling efficiency (PDCE) between a SS-SOA and optical fiber is also evaluated by measuring the photo-current of the active layer for TE and TM input signals. It is possible, therefore, to specify the polarization characteristics of the active region and spot-size converter region, which are indispensable parameters for the design of the SS-SOA.
Ken TSUZUKI Tadao ISHIBASHI Hiroshi YASAKA Yuichi TOHMORI
We have developed a traveling-wave optical modulator using an n-i-n heterostructure fabricated on an InP substrate. The modulation characteristics are studied theoretically and experimentally. We obtained an extremely small π voltage (Vπ) of 2.2 V, even for a short signal-electrode length of 3 mm. We confirmed a wide frequency bandwidth and clearly open eye diagrams at 40 Gbit/s.
Takeshi KUROSAKI Toshikazu HASHIMOTO Noboru ISHIHARA Yasuhiro SUZUKI Masahiro YANAGISAWA Hideaki KIMURA Makoto NAKAMURA Yuichi TOHMORI Kazutoshi KATO Yoshihiro KAWAGUCHI Yuji AKAHORI Yasufumi YAMADA Kuniharu KATO Hiromu TOBA Junichi YOSHIDA
This paper describes design techniques for suppressing crosstalk in an optical transceiver module using PLC-hybrid-integration technologies and for achieving burst-mode operation with high sensitivity and wide dynamic range using CMOS-IC technologies. An arrangement that reduces the electrical crosstalk to less than -100 dB was designed using three-dimensional electromagnetic field analysis. The configurations of a newly developed instantaneous-response CMOS LD driver circuit is also described and instantaneous-response CMOS receiver circuit techniques are reviewed. With these techniques, we have succeeded in building optical transceiver modules for ATM-PON systems using PLC-hybrid-integration and inexpensive standard CMOS-IC fabrication processes. Under full-duplex operation at 156 Mb/s, fabricated transceiver modules showed receiver sensitivity of better than -34 dBm and dynamic range of over 28 dB, which satisfy both the class-B and class-C specifications recommended by ITU-T (International Telecommunication Union-Telecommunication standardization sector) G983.1 for the optical transceiver module for an ONU (optical network unit).
Linda POSADAS Yuichi TOHMORI Kazuhiro KOMORI Shigehisa ARAI Yasuharu SUEMATSU
Direct modulation characteristics, such as the side mode suppression ratio and the dynamic wavelength shift, of BIG-DBR (Bundle Integrated Guide Distributed Bragg Reflector) lasers were investigated by applying both sinusoidal and pulse-like modulations to two different kinds of samples with 100 µm and 200 µm active region lengths. The higher side mode suppression ratio of more than 30 dB was obtained for the sample with short active region length of 100 µm within all the frequency range up to 2 GHz even under pulse-like modulation, whereas the dynamic wavelength shift became larger than that of longer active region sample.
Takeshi KITAGAWA Yuji AKAHORI Ikuo OGAWA Yuichi TOHMORI
We describe hybrid integration technologies that employ silica-based planar lightwave circuit (PLC) platforms, and report several high-performance optical components based on these technologies. First, we describe the requirements for optical integrated circuits. Then, we discuss the technologies used in hybrid integration, namely optical coupling between a semiconductor optical device and a silica waveguide, electrical signal transmission to the semiconductor optical device, and high quality optical signal processing. In addition, we describe optical integrated circuits developed for short- and long-haul networks. We realized these high-performance integrated components by combining appropriate hybrid integration technologies.
Yuichi TOHMORI Kazuhiro KOMORI Shigehisa ARAI Yasuharu SUEMATSU Hiromi OOHASHI
Wavelength-tunable 1.5 µm GaInAsP/InP bundle-integrated-guide distributed Bragg reflector (BIG-DBR) dynamic-single-mode lasers are presented. Tuning is due to free carrier plasma effect generated by the injected tuning current at the monolithically integrated tuning regions. Low threshold current CW operation of 28 mA was obtained in junction-up mounting. Wide-range continuous wavelength tuning more than 9 was demonstrated for the first time.
Takeshi KUROSAKI Toshikazu HASHIMOTO Noboru ISHIHARA Yasuhiro SUZUKI Masahiro YANAGISAWA Hideaki KIMURA Makoto NAKAMURA Yuichi TOHMORI Kazutoshi KATO Yoshihiro KAWAGUCHI Yuji AKAHORI Yasufumi YAMADA Kuniharu KATO Hiromu TOBA Junichi YOSHIDA
This paper describes design techniques for suppressing crosstalk in an optical transceiver module using PLC-hybrid-integration technologies and for achieving burst-mode operation with high sensitivity and wide dynamic range using CMOS-IC technologies. An arrangement that reduces the electrical crosstalk to less than -100 dB was designed using three-dimensional electromagnetic field analysis. The configurations of a newly developed instantaneous-response CMOS LD driver circuit is also described and instantaneous-response CMOS receiver circuit techniques are reviewed. With these techniques, we have succeeded in building optical transceiver modules for ATM-PON systems using PLC-hybrid-integration and inexpensive standard CMOS-IC fabrication processes. Under full-duplex operation at 156 Mb/s, fabricated transceiver modules showed receiver sensitivity of better than -34 dBm and dynamic range of over 28 dB, which satisfy both the class-B and class-C specifications recommended by ITU-T (International Telecommunication Union-Telecommunication standardization sector) G983.1 for the optical transceiver module for an ONU (optical network unit).