Patent Issued for Multi-Wavelength Semiconductor Laser Device

The patent's assignee for patent number 8891581 is Mitsubishi Electric Corporation (Tokyo, JP). News editors obtained the following quote from the background information supplied by the inventors: "An optical disc such as a compact disc (CD), a digital versatile disc (DVD), and a 'Blu-ray Disc.TM.' (BD) has been increasingly used now as large capacity storage media. Laser diodes used for reading/writing from/to these discs have respective different emission wavelengths: a CD laser diode has an emission wavelength of 780 nm band (infrared), a DVD laser diode has an emission wavelength of 650 nm band (red), and a BD laser diode has an emission wavelength of 405 nm band (blue-violet). Hence, in order to treat data for a CD, a DVD, and a BD in a single optical disc drive, required are three light sources of infrared, red, and blue-violet. "In a case of configuring a multi-wavelength semiconductor laser device such that different wavelength laser-diode chips are arranged side by side, their emission points are spaced largely apart from each other, resulting in difficulty in optical design. For dealing therewith, there has been a conventional multi-wavelength semiconductor laser device, in which red and infrared laser diodes are arranged in parallel and bonded on a blue-violet laser diode that is mounted on a heat sink, to be able to treat data for CD, DVD, and BD in a single optical disc drive (see, for example, JP 2006-59471A). "In the multi-wavelength semiconductor laser device described in JP 2006-59471A, however, since the infrared and the red laser diodes are bonded on the blue-violet laser diode, there has been a problem in that heat generated during operation of the infrared and the red laser diodes cannot efficiently dissipate to the heat sink. Moreover, this configuration makes their assembly process complicated, resulting in a problem of high manufacturing costs." As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventor's summary information for this patent: "The present invention is made to resolve such problems as mentioned above, and provides a multi-wavelength semiconductor laser device that has closely arranged laser-diode chips' emission points, and is easy in optical design and excellent in heat dissipation, as well as being easily manufactured. "A multi-wavelength semiconductor laser device according to a first aspect of the invention includes a block and a plurality of laser diodes whose emission wavelengths are different from each other, wherein the block is formed having a rectangular cross-section groove with a bottom face and two side faces extending in a predetermined direction, and the laser diodes are mounted on the bottom face and the side faces of the groove so that their laser beams emit in the predetermined direction. "A multi-wavelength semiconductor laser device according to a second aspect of the invention includes a block and a plurality of laser diodes whose emission wavelengths are different from each other, wherein the block is formed having a 'V'-shape cross-section groove with two side faces extending in a predetermined direction, and the laser diodes are mounted on both side faces of the groove so that their laser beams emit in the predetermined direction. "A multi-wavelength semiconductor laser device according to a third aspect of the invention includes a block and a plurality of laser diodes whose emission wavelengths are different from each other, wherein the block is formed having a rectangular projection, and the laser diodes are mounted on a top face and side faces of the projection. "A multi-wavelength semiconductor laser device according to a fourth aspect of the invention includes a block and a plurality of laser diodes whose emission wavelengths are different from each other, wherein the block is formed having a flat face and a projection extending from the flat face, and the laser diodes are mounted on the flat face of the block and side faces of the projection. "According to the invention, a multi-wavelength semiconductor laser device can be realized that has closely arranged laser-diode chips' emission points, and is easy in optical design and excellent in heat dissipation, as well as being easily manufactured." For additional information on this patent, see: Okura, Yuji. Multi-Wavelength Semiconductor Laser Device. U.S. Patent Number 8891581, filed January 29, 2014, and published online on November 18, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?