Initialization of phase-change optical recording medium

Abstract

A method of initializing a phase-change optical information recording medium is provided, using an optical system incorporating a semiconductor laser device. The laser device is characterized by a specified spatial power distribution. In a spatial distribution of the laser power focused on the recording medium, in the direction perpendicular to guide tracks the laser device preferably has less average smaller in both end regions of the spatial distribution, which have each 10% of the width at half maximum of the distribution, than the average in the center region of the full width at half maximum of the distribution.

1. A method of initializing a phase-change optical information recording medium, comprising the steps of:
 providing a semiconductor laser device;  
 providing an optical system including said semiconductor laser device configured to be utilized for initializing said phase-change optical information recording medium; and  
 irradiating at least a part of said phase-change optical information recording medium by means of light beams emitted from said semiconductor laser device;  
 wherein,  
 in the spatial distribution of the semiconductor laser power focused on said recording medium in the direction perpendicular to guide tracks, said semiconductor laser device has an average laser power in a first end region with a first predetermined width, and a second end region with a second predetermined width, of the width at half maximum of the spatial distribution, smaller than an average laser power in the center region of the full width at half maximum of the spatial distribution.  
 
     
     
       2. The method of initializing a phase-change optical information recording medium according to  claim 1 , wherein
 said first predetermined width is at 0% to 10% of the width at half maximum of the spatial distribution and said second predetermined width is at 90% to 100% of the width at half maximum of the spatial distribution.  
 
     
     
       3. The method of initializing a phase-change optical information recording medium according to  claim 1 , wherein
 said step of providing said semiconductor laser device includes polishing edge surfaces of at least one of an active layer and a reflective layer of said semiconductor laser device, substantially perpendicular to the direction of the laser emission, such that an  the average of the  laser power in at least one of the end regions of the laser power distribution at 0% to 10% and 90% to 100% of the width at half maximum of the spatial distribution is smaller than an  the average of  laser power in the center region of the full width at half maximum of the spatial distribution.  
 
     
     
       4. The method of initializing a phase-change optical information recording medium according to  claim 1 , further comprising the step of:
 providing at least one optical device in said optical system, configured to attenuate the light beams emitted from said semiconductor laser device such that an  the average of the  laser power in at least one of the end regions of the laser power distribution ranging at 0% to 10% and 90% to 100% of the width at half maximum of the spatial distribution is smaller than an  the average of  laser power in the center region of the full width at half maximum of the spatial distribution.  
 
     
     
       5. The method of initializing a phase-change optical information recording medium according to  claim 4 , wherein
 said optical device is an optical filter.  
 
     
     
       6. The method of initializing a phase-change optical information recording medium according to  claim 1 , wherein
 said semiconductor laser device is cured by energizing for at least about six hours with at least about 80% of a maximum allowable electric power prior to said initializing said recording medium such that an  the average of the  laser power in at least one of the end regions of the laser power distribution at 0% to 10% and 90% to 100% of the width at half maximum of the spatial distribution is obtained to be smaller than an  the average of  laser power in the center region of the full width at half maximum of the spatial distribution.  
 
     
     
       7. The method of initializing a phase-change optical information recording medium according to  claim 1 , wherein
 a distance of the laser device displacement perpendicular to the guide tracks per disk rotation is larger than one half of; and smaller than, the width at half maximum of the spatial laser power distribution of said light beams on said recording medium.  
 
     
     
       8. The method of initializing a phase-change optical information recording medium according to  claim 7 , wherein
 said semiconductor laser device has laser emissions having a width at half maximum of at least 80 microns of the spatial power distribution on said recording medium in the direction perpendicular to guide tracks.  
 
     
     
       9. A method of initializing a phase-change optical information recording medium comprising the steps of:
 directing an energy beam at a phase-change optical information recording medium;  
 causing relative motion between the beam and the medium;  
 said relative motion causing the beam to irradiate successive bands of the medium that partly overlap; and  
 said beam having a power distribution and said overlap being to a degree causing the irradiated areas of the medium to receive substantially the same cumulative energy from the beam despite said overlap.  
 
     
     
       10. A method as in  claim 9  in which said energy beam is a laser beam generated at a laser device. 
     
     
       11. A method as in  claim 10  including the step of polishing the laser device to achieve a laser beam power distribution configured to achieve said substantially same cumulative amount of energy despite said overlap. 
     
     
       12. A method as in  claim 10  including the step of filtering the laser beam prior to its reaching the medium to achieve a laser beam power distribution configured to achieve said substantially same cumulative amount of energy despite said overlap. 
     
     
       13. A method as in  claim 10  including the step of curing the laser device prior to initializing the medium to alter the power distribution of the laser beam to a distribution achieving said substantially same cumulative amount of energy despite said overlap. 
     
     
       14. An apparatus for initializing a phase- change optical information recording medium, comprising:      a semiconductor laser device configured to irradiate the phase - change optical information recording medium with a light beam to initialize the phase - change optical information recording medium;        wherein in the spatial distribution of the semiconductor laser power focused on said recording medium in the direction perpendicular to guide tracks, said semiconductor laser device has an average laser power in a first end region with a first predetermined width, and a second end region with a second predetermined width, of the width at half maximum of the spatial distribution, smaller than an average laser power in the center region of the full width at half maximum of the spatial distribution; and        wherein the semiconductor laser comprises at least one of an active layer and a reflection layer, and wherein a surface of the at least one of an active layer and an reflection layer perpendicular to an emitting surface of the semiconductor laser is polished.     
     
     
       15. The apparatus according to  claim 14 , wherein the first predetermined width is at  0 %  to  10   %  of the width at half maximum of the spatial distribution and the second predetermined width is at  90   %  to  100   %  of the width at half maximum of the spatial distribution.