Decemb er 10, 2010 / Vol. 8, No. 12 / CHINESE OPTICS LETTERS 1135
Method for eliminating mismatching error in monolithic
triaxial ring resonators
Xingwu Long (龙龙龙兴兴兴武武武) and Jie Yuan (袁袁袁 杰杰杰)
∗
Department of Opto electronic Engineering, College of Optoelectronic Science and Engineering,
National University of Defense Technology, Changsha 410073, China
∗
E-mail: jieyuan@nudt.edu.cn
Received April 22, 2010
Several results on optical-axis perturbation and elimination of the mismatching error C of a monolithic
triaxial ring resonator (MTRR) are rep orted. Based on the augmented 5×5 ray matrix method, by
simultaneously considering axial displacement of a mirror and the misalignments in three planar square
ring resonators of a MTRR, the rules of optical-axis perturbation are obtained. The mismatching error
C of the MTRR is eliminated. The results obtained are important for cavity design, as well as in the
improvement and alignment of MTRR.
OCIS codes: 140.4780, 140.3410, 140.3370, 140.3560.
doi: 10.3788/COL20100812.1135.
This letter is a continuation of Ref. [1]. Ring laser has
been used as a rotate sensor. The planar or non-planar
resonator, as well as monoaxial or monolithic triaxial
ring resonator (MTRR), have been widely used for laser
gyroscopes
[2−9]
. Continuous research on optical-axis per-
turbation in ring resonators have been conducted
[10−15]
.
However, the perturbation sources in all the previous ar-
ticles have been on radial displacements or angular mis-
alignments of the optical components of the ring res-
onator. The perturbation source of the axial displace-
ment of a mirror has not been previously discussed. The
augmented 5×5 ray matrix method is used to handle
these perturbation sources.
The ray matrix of a general optical component with
angular misalignment and radial displacements has the
form:
r
ox
r
0
ox
r
oy
r
0
oy
1
=
A
x
B
x
0 0 E
x
C
x
D
x
0 0 F
x
0 0 A
y
B
y
E
y
0 0 C
y
D
y
F
y
0 0 0 0 1
r
ix
r
0
ix
r
iy
r
0
iy
1
, (1)
where r
ix
, r
iy
, r
ox
, and r
oy
are the input ray and out-
put ray heights from the reference axis along the x and
y axes; this is referred to as optical-axis decentration.
Then, r
0
ix
, r
0
iy
, r
0
ox
, and r
0
oy
are the angles that the in-
put and output rays construct with the reference axis in
the x and y planes, resp ectively; this is referred to as
optical-axis tilts. In Fig. 1, x axis has been chosen as an
example to show the parameters. A
x
, B
x
, C
x
, and D
x
are the standard ray-matrix elements in the tangential
plane; A
y
, B
y
, C
y
, and D
y
are the standard ray-matrix
elements in the sagittal plane; and E
x
and E
y
are the de-
centration terms representing radial displacements along
x and y axes. F
x
and F
y
are the tilt terms represent-
ing the angular misalignments. In the case of a mirror,
F
x
= 2 tan(θ
x
), F
y
= 2 tan(θ
y
), and θ
x
and θ
y
are the
misalignment angles in its local tangential and sagittal
planes, respectively.
In Fig. 2
[1]
, a spherical mirror has been chosen as an
example to show the perturbation sources. M and M
0
represent the mirrors before and after axial displacement
δ along the normal z direction. Axes x and y are perpen-
dicular to z. Generally, the mirror has six movements,
which are the displacements along the x, y, and z axes,
and the rotations around the x, y, and z axes. The trans-
lation of the mirror along the x and y axes manifests as
radial displacements represented by E
x
and E
y
in the
augmented 5×5 matrix.
The rotary movements around the axes of x and y are
the angular misalignments of the mirror, and they can
be represented by the terms F
y
and F
x
in the augmented
5×5 matrix. The rotation of the mirror around the axis z
can be ignored because it has spherical symmetry. In this
letter, the displacement of the mirror along the z axis is
called axial displacement. It cannot be represented by
any term in the augmented 5×5 matrix in the current
framework of the study. Thus far, this axial displacement
has not been discussed in detail.
In this letter, the axial displacement of the mirror is
treated as the source of p erturbation along with the mis-
alignments. The augmented 5×5 ray matrix is modified
to include this perturbation. To the best of our knowl-
edge, this is the first time that such axial displacement
has been considered as a perturbation source. The square
ring resonator and MTRR are chosen as examples to
show its application. Optical-axis perturbation induced
by the axial displacement of the spherical mirror and the
corresponding misalignments can be obtained by utilizing
the modified 5×5 ray matrix. The method for reducing,
Fig. 1. Schematic diagram of the input and output rays.
1671-7694/2010/121135-04
c
° 2010 Chinese Optics Letters