Browse Prior Art Database

Full-Wafer Laser Beam Measurements

IP.com Disclosure Number: IPCOM000099981D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 73K

Publishing Venue

IBM

Related People

Bona, GL: AUTHOR [+2]

Abstract

With the advent of semiconductors having etched mirror facets, it is possible to access the important laser parameters before parting the individual lasers off the wafer. To determine the quality of a laser beam while still "on-wafer", a reflecting surface is formed in front of the etched laser facet, parallel to the plane of the active layer of the laser. This surface provides a so-called Lloyd's mirror [*]. Since portions of the beam are reflected at the mirror, the far-field pattern of the laser is considerably affected compared to a beam from a separated laser. This allows the measurement of the wavelength and the distance between the Lloyd's mirror surface and the active layer.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 59% of the total text.

Full-Wafer Laser Beam Measurements

       With the advent of semiconductors having etched mirror
facets, it is possible to access the important laser parameters
before parting the individual lasers off the wafer.  To determine the
quality of a laser beam  while still "on-wafer", a reflecting surface
is formed in front of the etched laser facet, parallel to the plane
of the active layer of the laser.  This surface provides a so-called
Lloyd's mirror [*].  Since portions of the beam are reflected at the
mirror, the far-field pattern of the laser is considerably affected
compared to a beam from a separated laser.  This allows the
measurement of the wavelength and the distance between the Lloyd's
mirror surface and the active layer.

      Fig. 1 shows the far-field pattern 1 produced by the beam from
a laser diode 2 with a Lloyd's mirror as measured on the wafer 3.
The pattern is due to the reflection of part of the light beam at the
mirror and subsequent interferences with the direct, unreflected
light from the laser facet.  The dotted curve 4 illustrates the
far-field pattern as produced by the same laser after dicing the
laser, i.e., with the mirror removed.

      Fig. 2 depicts the paths of light rays emitted from the
semiconductor laser 2: ray 5* bouncing off from mirror surface 6 and
interfering with direct ray 5.  The interference pattern can be
calculated analytically since the situation is equivalent to two
lasers separated by a distance 2D; D bei...