Nec Corporation

Masayoshi Tsuji

Naofumi Suzuki

Kikuo Makita

Kenichiro Yashiki

Hiroshi Hatakeyama

Kimiyoshi Fukatsu

Takayoshi Anan

Takeshi Akagawa

Koji Kudo

Wataru Hattori

Shuhei Yoshida

Masahiro Tanomura

Yoshitaka Yokoyama

A wireless power feeding system capable of long distance and highly efficient space transmission of power is provided. A wireless power feeding system includes a power transmitter, a power receiver, and a power receiving body. The power transmitter generates electromagnetic waves. The power receiver is supplied with power by means of the electromagnetic waves received from the power transmitter using a magnetic field resonance phenomenon. The power receiving body is inserted into an electromagnetic field created by the power transmitter and the power receiver, and receives power by means of the electromagnetic field.

Wireless power feeding system and wireless power feeding method

The present invention provides a surface-emission type semiconductor laser wherein an effective length of a cavity is reduced, thereby enabling to realize a higher-speed direct modulation. In the surface-emission type semiconductor laser according to the present invention, when supposing the optical path length (L) of a resonator part relative to a lasing wavelength &#x3bb;to be given as 0.9&#xd7;&#x3bb;&#x2266;L&#x2266;1.1&#xd7;&#x3bb;, and denoting the refractive indexes of a high refractive index layer and a low refractive index layer of a dielectric DBR by nand n; the average refractive index within an optical path length &#x3bb;/4 in the semiconductor in contact with the dielectric DBR by n; and the refractive indexes of the high refractive index layer and the low refractive index layer of a semiconductor DBR by nand n, respective materials to be used are selected so as to satisfy the following conditions (1) and (2):()()(),&#x2003;&#x2003;(1)

Surface-emission type semiconductor laser

An optical communication system for performing data transmission with optical signals comprises a first optical transmitter and a first optical receiver. The first optical transmitter has a first surface-emitting laser including an active layer of a multiple quantum well structure having a quantum well layer of InGaAs (0.15&#x2266;x&#x2266;0.35), the first surface-emitting laser having an oscillation wavelength ranging from 1000 nm to 1100 nm inclusive. The first optical transmitter transmits an optical signal generated by the first surface-emitting laser. The first optical receiver is connected to the first optical transmitter by a first optical transfer path, and receives the optical signal transmitted from the first optical transmitter through the first optical transfer path.

Optical communication system and optical transmitter

A surface emitting laser is provided with a first multilayer Bragg reflecting mirror including a first layer, a second multilayer Bragg reflecting mirror including a second layer, and an optical resonator unit that is held between these multilayer Bragg reflecting mirrors and includes an active layer. Further, the optical resonator unit contacts with the first layer and second layer respectively. The effective refraction index nof the resonator unit is larger than either the first layer or the second layer, and an optical length nL of the optical resonator unit has a relationship with an oscillating wavelength &#x3bb; of the surface emitting laser to satisfy the following relationship: 0.5&#x3bb;&#x3c;nL&#x2266;0.7&#x3bb;.

Surface emitting laser

In an avalanche photodiode having a separated electron injection type light absorbing layer/multiplication layer structure, the multiplication layer comprises In Al Ga As with the composition thereof being graded from InAlAs on the light absorbing layer side to InGaAs and preferably has a thickness of not more than 0.1 &mgr;m. By virtue of the above construction, very low noise characteristics and ultraspeed characteristics can be attained in photodetectors at 1 &mgr;m wavelength for long distance optional communications.

Ultraspeed low-voltage drive avalanche multiplication type semiconductor photodetector

A semiconductor photonic element is provided, which realize low threshold current and satisfactory characteristics in the high temperatures and/or high output operating condition. This element is comprised of (a) a semiconductor substrate; (b) a mesa structure formed on a first surface of the substrate to extend in a specific direction; the mesa structure including an active layer and a pair of p- and n-type cladding layers located respectively at top and bottom sides of the active layer, forming a double heterojunction; (c)a current-constricting structure for constricting an injection current formed at each side of the mesa structure to expose a top of the mesa structure from the current-constricting structure; the current-constricting structure comprising a first current-blocking part and a second current-blocking part; the first current-blocking part having a dielectric current-blocking layer that extends to the mesa structure; the dielectric current-blocking layer being contacted with top edges of the mesa structure; the second current-blocking part having a semiconductor current-blocking layer; and (d) a semiconductor burying layer formed to cover the mesa structure and the multilayer current-constricting structure; the semiconductor burying layer being contacted with the top of the mesa structure.

Semiconductor photonic element, method of fabricating the same, and semiconductor photonic device equipped therewith

The invention provides a semiconductor optical modulation device which has low power dissipation, high extinction ratio and high speed response features. An n-type InP clad layer, an n.sup.- -type InAlAs-InAlGaAs composition inclination multiple layer, a p-type InP clad layer and a p.sup.+ -type InGaAs contact layer are layered on an n-type InP substrate. The layers are etched up to an intermediate location of the n-type clad layer to form a rib waveguide, and a positive electrode is formed on an upper portion of the rib waveguide. Further, a negative electrode is formed on the substrate.

Semiconductor optical modulation device

An avalanche photodiode is provided which consists of a staircase APD with a periodic multilayer structure graded in composition from InAlAs to InGa.sub.x Al.sub.(1-x) As (x&gt;0.1) as the multiplication layer to improve the dark current characteristic. Another photodiode with separate photoabsorption and multiplication regions is provided with an electric-field relaxation layer whose bandgap is wider than that of the photoabsorption and has a triple structure with a highly-doped layer sandwiched between lightly-doped layers. This photodiode incorporates in detail on an n-type InP substrate, an avalanche multiplication layer 13 of a periodic multilayer structure graded in composition from n.sup.- -InAlAs to InGa.sub.x Al.sub.(1-x) As, a p.sup.- -InGaAs photoabsorption layer 17, and an InP electric-field relaxation triple layer 16 consisting of n.sup.-, p.sup.+, and p.sup.- layers between the avalanche multiplication layer 13 and the photoabsorption layer 17.

Staircase avalanche photodiode

On a p-type InP substrate 12, there are provided a p-type InGaAs light absorptive layer 14 and an InAlAs/InGaAs superlattice avalanche multiplier layer 15. By selecting the composition of the well layer and the barrier layer of the avalanche multiplier layer 15, a strain is applied to at least one of them so that the difference .DELTA. Ec between the energies at the lower end of the conduction band of the well layer and/or the barrier layer is increased, or the difference .DELTA. Ev between the energies at the upper end of the valence band of the well layer and/or the barrier layer is decreased, and/or the effective mass of the hole within the well layer and/or barrier layer is decreased. Thus, the ionization factor ratio is further improved, or the pile-up of the hole is alleviated, or the traveling time of the hole is shortened to achieve an avalanche multiplier semiconductor photodetector having a wide bandwidth, low noise and high response characteristic.

Semiconductor photodetector using avalanche multiplication and strained

An avalanche photodiode includes an avalanche multiplication layer of a hetero-periodical structure consisting of alternately provided barrier and well layers. Each barrier layer includes a multi-quantum barrier layer consisting of alternately provided short-width barrier and well layers. The barrier and well layers include respectively first and second III-group elements which meet the following conditions:

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Tokyo, Japan

Masayoshi Tsuji