Optical Module

Abstract

An optical module according to the invention can achieve an optical system using a transmission-type diffraction grating for bending the optical path of incident light with a specific wavelength by about 90°. A substrate of the transmission-type diffraction grating is mounted at an angle in a range of +5° with respect to the design incident angle α of the incident light. The optical system can be applied to a light multiplexing/demultiplexing module.

1 .- 9 . (canceled) 
   
   
       10 . An optical module comprising:
 an optical system using a diffraction optical element for bending an optical axis of an incident light beam with a specific wavelength at about 90°; and   a collimator for substantially collimating the light beam incident on the diffraction optical element.   
   
   
       11 . An optical module comprising:
 an optical system using a diffraction optical element for bending an optical axis of an incident light beam with a specific wavelength at about 90°; and   a converging device for converging the light beam output from the diffraction optical element.   
   
   
       12 . An optical module comprising:
 an optical system using a diffraction optical element for bending an optical axis of an incident light beam with a specific wavelength at about 90°;   a first cylindrical holding member having a first hollow portion;   a second cylindrical holding member having a second hollow portion;   a diffraction grating provided between the first and second cylindrical holding members;   a light input device held by the first holding member in the first hollow portion so that the first hollow portion forms an optical path of incident light; a diffracted light detection device connected to an end portion of the second holding member opposing to the diffraction grating so that the hollow portion of the second holding member forms an optical path of diffracted light; and   wherein the diffraction grating is fixed so that a light incidence surface of the diffraction grating abuts on an end portion of the first holding member and a light output surface of the diffraction grating abuts on an end portion of the second holding member.   
   
   
       13 . An optical module according to  claim 12 , wherein a sum of the angle between an end surface at the end portion of the first holding member abutting on the diffraction grating and a axial direction of the cylinder of the first holding member and an angle between an end surface at the end portion of the second holding member abutting on the diffraction grating and an axial direction of the cylinder of the second holding member is within a range of an angle between the incident light and the diffracted light. 
   
   
       14 . An optical module according to  claim 12 , wherein the light input device includes a collimator. 
   
   
       15 . An optical module according to  claim 12 , wherein the second holding member holds a converging device in the second hollow portion. 
   
   
       16 . An optical module according to  claim 14 , wherein the first holding member has a mechanism for adjusting the collimator. 
   
   
       17 . An optical module according to  claim 12 , wherein a connection portion between the second holding member and the diffracted light detection device is fitted to a holding member for holding the diffracted light detection device so that the connection portion rotates around the optical axis. 
   
   
       18 . An optical module according to  claim 12 , wherein the number N of grooves in the transmission-type diffraction grating is represented by the formula:
     N =.±.(cos α+sin α)/( m λ)   in which .±. is the same sign as that of m when an mth-order diffracted light beam (m is an integer) is used in the condition that incident light with a wavelength λ contained in the light inputted from the light input device is made incident at an incident angle α on the transmission-type diffraction grating.   
   
   
       19 . An optical module according to  claim 12 , wherein the light input device has an optical fiber, and a planoconvex lens. 
   
   
       20 . An optical module according to  claim 12 , wherein the light input device has an optical fiber, and a graded index rod lens. 
   
   
       21 . An optical module according to  claim 15 , wherein the converging device is a planoconvex lens. 
   
   
       22 . An optical module according to  claim 12 , wherein the diffracted light detection device is a photodetector array.