Blazed diffraction grating structures and method of manufacturing the same

• US 4,330,175 A
• Filed: 07/17/1979
• Issued: 05/18/1982
• Est. Priority Date: 07/18/1978
• Status: Expired due to Term

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Minowa, Junichiro, Fujii, Yohji
• Primary Examiner(s): Evans, F. L.
• Assistant Examiner(s): ARNOLD, BRUCE
• Application Number:
  US06/058,382
• Time in Patent Office: 1,036 Days
• Field of Search: 427/162, 427/163, 156/647, 156/651, 350/162 R
• US Class Current: 359/571
• CPC Class Codes: G02B 5/1857 using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams
• CPC Class Codes: G02B 5/1861 Reflection gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence
• CPC Class Codes: H01L 21/30608 Anisotropic liquid etching H01L21/3063 takes precedence
• CPC Class Codes: Y10S 438/978 forming tapered edges on substrate or adjacent layers
• CPC Class Codes: Y10T 156/1028 by bending, drawing or stretch forming sheet to assume shape of configured lamina while in contact therewith

Abstract

In a diffraction grating made of a single crystalline silicon substrate, one major plane thereof is provided with a plurality of asymmetric triangular grooves, each having a wall inclined by an angle θ with respect to the major surface so as to satisfy an equation ##EQU1## where θ represents the blaze angle, P the pitch of the groove, λ_B the blazing wavelength, and m the order of diffraction. The walls of each groove receiving incident light is covered with a metal coat.

The diffraction grating is prepared by using a {hkl} plane (where h=k) inclined by θ with respect to the {111} plane of the single crystalline silicon as a major surface, and then anisotropic-etching the major surface through an etching mask having stripes having sufficiently smaller width than the grating constant. Preferably, following the anisotropic etching, isotropic etching is made for the major surface.

Claims

1. A diffraction grating structure comprising a planar diffraction grating including a single crystalline silicon substrate having a major surface {hkl} (where h=k) provided with a plurality of triangular grooves at a pitch of P, each groove having an asymmetric cross-sectional shape and {111} planes as walls of each groove formed in the major surface {hkl} which is inclined by an angle of θ

with respect to the {111} plane so as to satisfy the equation

space="preserve" listing-type="equation">θ

=sin mλ

.sub.B /2P

where θ

represents a blaze angle, P the pitch of the groove, λ

_B the blaze wavelength and m the order of diffraction;

a metal coat layer having a uniform thickness and applied to the walls of each of said triangular grooves upon which light is incident; and

wherein said planar diffraction grating is flexed below its elasticity limit to obtain a curved diffraction grating structure.