Harmonic generator, method for driving harmonic generator, image-displaying apparatus, image-forming apparatus, optical storage apparatus that employs harmonic generator

Abstract

There is provided a harmonic generator generates high power laser light and can be modulated at high modulation rate. The semiconductor laser emits a first output light when a bias current is supplied, and a second output light when a modulating current is superposed to the bias current. On of the first output lights has a wavelength inside of a wavelength tolerance of phase-matching of the wavelength-converting element. The other has a wavelength outside of the wavelength tolerance of phase-matching.

1 . A harmonic generator comprising a semiconductor laser and a wavelength-converting element comprised of a non-linear optical material that converts a wavelength of an output light emitted by the semiconductor laser into a harmonic, 
 wherein the semiconductor laser emits a first output light when a bias current is supplied and a second output light when a pulse modulating current is superposed to the bias current, the first output light and the second output light being different from each other in wavelength,    wherein one of wavelengths of the first output light and the second output light is in an allowable range of phase-matching wavelengths of the wavelength-converting element and the other is out of the allowable range, and    wherein modulation of the second output light is carried out by modulating a pulse width of the pulse modulating current.    
     
     
         2 . A method for driving a harmonic generator in which an output light of a semiconductor laser is incident on a wavelength-converting element comprised of a non-linear optical material to generate a harmonic, comprising the steps of: 
 supplying to the semiconductor laser a driving current comprised of a bias current and a pulse modulating current superposed on the bias current so that the output light of the semiconductor laser is modulated, wherein an oscillation wavelength of the output light of the semiconductor laser is out of an allowable range of phase-matching wavelengths when only the bias current is supplied, and is in the allowable range when both of the bias current and the pulse modulating current are supplied, and    wherein the modulation of the output light of the semiconductor laser is carried out by modulating a pulse width of the pulse modulating current.    
     
     
         3 . (canceled)  
     
     
         4 . The harmonic generator according to  claim 1 , wherein the harmonic has a light power having a modulation waveform and an amplitude that varies from zero to a predetermined value.  
     
     
         5 . The harmonic generator according to  claim 1 , wherein the non-linear optical material is a ferroelectric crystal that performs wave conversion using birefringent phase matching.  
     
     
         6 . The harmonic generator according to  claim 1 , wherein the non-linear optical material is a non-linear optical material obtained by polarizing a glass material.  
     
     
         7 . The harmonic generator according to  claim 1 , wherein the non-linear optical material is an organic material.  
     
     
         8 . The harmonic generator according to  claim 1 , wherein the non-linear optical material has a periodically poled structure.  
     
     
         9 . The harmonic generator according to  claim 1 , wherein the non-linear optical material has an optical resonator construction.  
     
     
         10 . The harmonic generator according to  claim 1 , wherein the wavelength-converting element is comprised of an optical waveguide comprised of a non-linear optical material.  
     
     
         11 . The harmonic generator according to  claim 1 , wherein the semiconductor laser generates light at the range of 980 to 1200 nm wavelength.  
     
     
         12 . The harmonic generator according to  claim 11 , wherein the semiconductor laser includes an active region having an InGaAs strained quantum well.  
     
     
         13 . The harmonic generator according to  claim 11 , wherein the semiconductor laser includes an active region having a GaInNAs compound semiconductor.  
     
     
         14 . The harmonic generator according to  claim 11 , wherein the semiconductor laser includes an active region having a GaAsSb compound semiconductor.  
     
     
         15 . The harmonic generator according to  claim 1 , wherein the semiconductor laser includes an active region having an AlGaAs compound semiconductor.  
     
     
         16 . The harmonic generator according to  claim 1 , wherein the semiconductor laser is a Fabry-Perot type semiconductor laser which has a light-emitting surface that serves as a resonator mirror.  
     
     
         17 . The harmonic generator according to  claim 1 , wherein the semiconductor laser is either a distributed Bragg reflection semiconductor laser or a distributed feedback semiconductor laser which have a waveguide grating as a resonator mirror.  
     
     
         18 . An image displaying apparatus comprising: 
 a light source for emitting light;    a lens for transmitting the light emitted from the light source;    a deflector for deflecting the light transmitted by the lens onto a screen,    wherein the light source comprises the harmonic generator according to  claim 1 .    
     
     
         19 . An image forming apparatus comprising: 
 a light source for emitting light;    a first lens for transmitting the light emitted from the light source;    a deflector for deflecting the light transmitted by the first lens;    a second lens for transmitting the light deflected by the deflector onto an image forming surface,    wherein the light source comprises the harmonic generator according to  claim 1 .    
     
     
         20 . An optical recording apparatus comprising: 
 a unit for reading and writing data from an optical disk memory,    wherein the unit comprises the harmonic generator according to  claim 1.