Nippon Telegraph and Telephone Corporation

Ntt Electronics Corporation

Nobuhiro Kikuchi

Yasuo Shibata

Naoki Fujiwara

Josuke Ozaki

Yoshihiro Ogiso

Ken Tsuzuki

Eiichi Yamada

Nobuhiro Nunoya

Hiromi Oohashi

Yuichi Tomori

Tadao Ishibashi

Hiroshi Yamazaki

Kenji Kobayashi

Yuichi Thomori

Shinsuke Nakano

Masahiro Suzuki

Hiroshi Koizumi

Hideyuki Nosaka

Koichi Murata

Hiroyuki Uzawa

Munehiko Nagatani

Hiroyuki Fukuyama

Takashi Saida

Shin Kamei

Hiromasa Tanobe

Kengo Horikoshi

Hiroto Kawakami

Yuta Ueda

Hiroshi Tomita

Hiroaki Katsurai

Shigeru Kanazawa

Toshihiro Itoh

Tomoyoshi Kataoka

Shigeki Aisawa

Masafumi Nogawa

Kazuhiro Maruyama

Mikio Yoneyama

Mitsuteru Ishikawa

Hiroyasu Mawatari

Masaki Kohtoku

Norihide Kashio

Tomoyuki Akeyoshi

Yves Bouvier

In a terminator, a midpoint electrode is provided between a first signal electrode and a second signal electrode, a first resistor is connected between the first signal electrode and the midpoint electrode, a second resistor is connected between the second signal electrode and the midpoint electrode, a first GND electrode is provided on a side opposite to the side where the first resistor is provided with the first signal electrode interposed therebetween, a second GND electrode is provided on the side opposite to the side where the second resistor is provided with the second signal electrode interposed therebetween, and capacitances in the terminator are formed between the first signal electrode and the midpoint electrode, between the second signal electrode and the midpoint electrode, between the first signal electrode and the first GND electrode, and between the second signal electrode and the second GND electrode.

Optical modulator module

Provided is an optical modulator having an optical modulation high frequency line through which a high frequency electrical signal can be efficiently input to an optical modulation region and which is in a broadband. High frequency lines of an optical modulator, that is, an input high frequency line, an optical modulation high frequency line, and an output high frequency line have a line configuration in which each of the input high frequency line and the output high frequency line is divided into a plurality of segments, and adjacent segments of the plurality of the segments have different characteristic impedances and propagation constants. The input high frequency line and the output high frequency line may be implemented by changing a width or a thickness of a signal electrode formed on a dielectric forming a micro-strip line between adjacent segments. The characteristic impedances and the propagation constants may be changed by changing a dielectric constant of the dielectric instead of changing the width or the thickness of the signal electrode.

Optical modulator

The present invention provides a highly reliable, high-speed, and low-loss semiconductor optical modulation element that protects a pin junction structure in a modulation region against reverse voltage ESD by configuring an additional capacity having a thyristor structure between a plurality of feeding pad electrodes. An n-type contact layer, an n-type cladding layer, a non-doped core/cladding layer, a p-type cladding layer, and a p-type contact layer are sequentially laminated on the substrate surface. A Mach-Zehnder interferometric waveguide and a plurality of feeding pad installation sections are formed by dry etching. The n-type contact layer and the n-type cladding layer are removed except for a modulation region of the Mach-Zehnder interferometric waveguide and a feeding region in which the feeding pad installation sections are formed so that the modulation region and the semiconductor of the lower part of the feeding region are electrically isolated from each other. The feeding pads are formed on the common n-type contact layer and n-type cladding layer. A thyristor structure of a pinip junction is formed between the feeding pads.

Semiconductor optical modulation element

This invention provides a high-frequency line adopting a structure to suppress an impedance variation and occurrence of an excessive power loss in high-frequency wiring having intersection with an optical waveguide. A high-frequency line is a microstrip line which has a basic configuration of stacking a ground electrode, a dielectric layer, and a signal electrode in this order on a SI-InP substrate. In addition, as shown in a transverse sectional view, an optical waveguide core made of InP-based semiconductor intersects with the high-frequency line in a crossing manner. A width of the signal electrode is partially increased in a certain region covering the intersection with the optical waveguide along a propagating direction of the high-frequency line. In the microstrip line, the width of the signal electrode is partially increased from wto w, and characteristic impedance is thus reduced as compared to one with the uniform width w.

High-frequency line

To provide a Mach-Zehnder (MZ) type semiconductor optical modulation element that can be used as a modulator, which is ultrafast and excellent in electrical stability. A semiconductor optical modulation element of a Mach-Zehnder type that performs modulation of light using a refractive index modulation region where a refractive index of the light guided to an optical waveguide is modulated and an input and output region where multiplexing/demultiplexing of the light split in the refractive index modulation region is performed, characterized in that in the refractive index modulation region of the optical waveguide, an n-type clad layer, an i core layer, and a p-type clad layer are stacked in the order from a top layer on a substrate surface equivalent to a (100) plane of a sphalerite-type seminsulating semiconductor crystal substrate, the n-type clad layer is formed in a ridge shape in an inverted mesa direction, and a capacitancl-oaded electrode is provided on the n-type clad layer.

An optical modulator driver circuit () includes an amplifier (, Q, Q, R-R), and a current amount adjustment circuit () capable of adjusting a current amount of the amplifier () in accordance with a desired operation mode. The current amount adjustment circuit () includes at least two current sources (IS) that are individually ON/OFF-controllable in accordance with a binary control signal representing the desired operation mode.

Optical modulator driver circuit and optical transmitter

A semiconductor optical modulator that includes a first semiconductor optical waveguide having a laminated structure including a core layer, a first clad layer, a second clad layer, and a barrier layer, the first clad layer and the second clad layer being disposed below and above the core layer, the barrier layer being inserted between the second clad layer and the core layer; a second semiconductor optical waveguide having a laminated structure in which the second clad layer has a p-type semiconductor penetrating locally through a n-type semiconductor in a laminated direction in the laminated structure of the first semiconductor optical waveguide; a first electrode connected to the first clad layer of the first semiconductor optical waveguide; and a second electrode electrically connecting the second clad layer of the first semiconductor optical waveguide and the p-type semiconductor of the second clad layer of the second semiconductor optical waveguide.

Semiconductor optical modulator and optical modulating apparatus

The present invention can provide an npin-type optical modulator that has a high withstand voltage and is easily fabricated. A semiconductor optical amplifier () according to an embodiment of the present invention is an npin-type semiconductor optical modulator in which layers are sequentially stacked, with a cathode layer (-) arranged on the substrate side, including at least a first n-type cladding layer (-), a p-type cladding layer (), a core layer () and a second n-type cladding layer (-). In this semiconductor optical modulator, the p-type cladding layer () is electrically connected to an electrode (-) of the cathode layer. Accordingly, the accumulation of holes in the p-type cladding layer associated with light absorption in the npin-type optical modulator can be absorbed in the electrode on the negative side. This npin-type semiconductor optical modulator can be comparatively easily fabricated using conventional semiconductor manufacturing techniques by adopting a mesa type waveguide structure.

Semiconductor optical modulator

An optical semiconductor device and optical semiconductor integrated circuit are provided by combining, on a semiconductor substrate, materials having different refractive indices and different temperature dependence of the refractive indices. In particular, it becomes possible to control the temperature dependence of the oscillation wavelength with a propagating region having a material and/or structure whose temperature dependence of the refractive index is different from that of a gain region of the semiconductor laser. In addition, they can be configured to have a plurality of interfaces formed along the waveguide direction of the optical waveguide so that the light reflected off the first interface is weakened by the light reflected from the remaining interfaces. Also, they can be configured with the interfaces inclined to the propagating direction so that the waveguide loss due to the reflection and refraction between the optical waveguides whose refractive indices differ from each other can be reduced.

Optical semiconductor device and optical semiconductor integrated circuit

There is provided a semiconductor optical modulator capable of performing a stable operation and having an excellent voltage-current characteristic to an electric field while exhibiting the characteristic of a semiconductor optical modulator with an n-i-n structure. The semiconductor optical modulator includes a waveguide structure that is formed by sequentially growing an n-type InP clad layer (), a semiconductor core layer () having an electro-optic effect, a p-InAlAs layer (), and an n-type InP clad layer (). An electron affinity of the p-InAlAs layer () is smaller than an electron affinity of the n-type InP clad layer (). In the waveguide structure having such a configuration, a non-dope InP clad layer () and a non-dope InP clad layer () may be respectively provided between the n-type InP clad layer () and the semiconductor core layer (), and between the semiconductor core layer () and the p-InAlAs layer ().

An integrated optical waveguide has a first optical waveguide, a second optical waveguide, and a groove. The second optical waveguide is coupled to the first optical waveguide and has a refractive index that is different from the first optical waveguide. The groove is disposed so as to traverse an optical path of the first optical waveguide and is separated from an interface between the first optical waveguide and the second optical waveguide by a predetermined spacing. The spacing from the interface and the width of the groove are determined such that reflection at a boundary between the first optical waveguide and the second optical waveguide is weakened. A semiconductor board may be disposed at a boundary between the first optical waveguide and the second optical waveguide. In this case, the width of the groove and the thickness of the semiconductor board are determined such that light reflected off an interface between the first optical waveguide and the groove is weakened by light reflected from an interface between the groove and the semiconductor board, and by light reflected from an interface between the semiconductor board and the second optical waveguide.

An integrated optical waveguide has first, second, and third optical waveguiding regions. The second optical waveguiding region has a refractive index different from that of the first optical waveguiding region. The second optical waveguiding region has an interface surface with the first optical waveguiding region that is inclined with respect to the waveguide direction of the first optical waveguiding region. The third optical waveguiding region has an interface surface with the second optical waveguiding region that is disposed such that a refraction direction through the interface surface is in line with the waveguide direction.

An optical amplifier includes a first optical path, second optical path, semiconductor optical amplifier, and multi-mode interference 3-dB coupler. The first optical path guides oscillation light. The second optical path guides signal light. The semiconductor optical amplifier causes oscillation on the first optical path. The multi-mode interference 3-dB coupler crosses the first and optical paths in the gain medium of the semiconductor optical amplifier.

Optical amplifier

Growing community of inventors

Zama, Japan

Nobuhiro Kikuchi