Non-reciprocal optical element for photonic devices

• US 6,611,644 B2
• Filed: 12/01/2000
• Issued: 08/26/2003
• Est. Priority Date: 11/17/1999
• Status: Expired due to Fees

• Current Assignee: Universite Laval
• Original Assignee: Universite Laval
• Inventors: Galstian, Tigran
• Primary Examiner(s): Robinson, Mark A.
• Assistant Examiner(s): Amari, Alessandro V
• Application Number:
  US09/726,536
• Publication Number:
  US 20010036011A1
• Time in Patent Office: 998 Days
• Field of Search: 385/15, 385/24, 385/37, 385/122, 385/1-3, 385/7
• US Class Current: 385/37
• CPC Class Codes: G02B 2006/12157 Isolator
• CPC Class Codes: G02B 6/02109 having polarization sensitive features, e.g. reduced photo-induced birefringence
• CPC Class Codes: G02B 6/02133 using beam interference
• CPC Class Codes: G02B 6/02152 involving moving the fibre or a manufacturing element, stretching of the fibre G02B6/02147 takes precedence
• CPC Class Codes: G02B 6/122 Basic optical elements, e.g. light-guiding paths
• CPC Class Codes: G02B 6/2746 comprising non-reciprocal devices, e.g. isolators, FRM, circulators, quasi-isolators magneto-optic non-reciprocal devices G02F1/093

Abstract

This invention relates to fabrication techniques for the creation of new optical elements, an asymmetric (non-reciprocal) diffraction grating and a passive nonlinear optical (visible, microwave, etc.) isolator (diode). It may have potential applications in the field of optical detection (spectrometers) and communications (circulators, wavelength division multiplexing circuits, etc.), etc. One of applications of this proposal is the significant reduction of the noise level in optical communication systems or any other optical systems using laser sources. Another potential interest of these diodes is the fabrication of integrated laser gyroscopes for applications in aviation, etc.

Claims

1. A non-reciprocal optical element comprising:

an optical medium coupled between a first port and a second port;

a first Bragg grating recorded in the optical medium as a periodic variation of a respective first optical property of the optical medium; and

a second Bragg grating recorded in the optical medium as a periodic variation of a respective second optical property of the optical medium, the second Bragg grating at least partially overlapping the first Bragg grating within the optical medium;

whereby light of a predetermined wavelength traversing the optical medium from the first port toward the second port is substantially reflected, and light of the same wavelength traversing the optical medium from the second port toward the first port is substantially not reflected.

2. A non-reciprocal optical element as claimed in claim 1, wherein:

the first Bragg grating is adapted to modulate an amplitude of light traversing the optical medium; and

the second Bragg grating is adapted to modulate a phase of light traversing the optical medium.

3. A non-reciprocal optical element as claimed in claim 2, wherein:

the first Bragg grating comprises periodic variations in an absorption of the optical medium; and

the second Bragg grating comprises periodic variations in a refractive index of the optical medium;

whereby the light is absorbed when passing from the second port to the first port.

4. A non-reciprocal optical element as claimed in claim 2, wherein:

the first Bragg grating comprises periodic variations in a gain of the optical medium; and

the second Bragg grating comprises periodic variations in a refractive index of the optical medium;

whereby the light is amplified when passing from the second port to the first port.

5. A non-reciprocal optical element as claimed in claim 1, wherein fringes of the first Bragg grating are separated from corresponding fringes of the second Bragg grating by a predetermined fringe shift.

6. A non-reciprocal optical element as claimed in claim 5, wherein the predetermined fringe shift is less than one period.

7. A non-reciprocal optical element comprising:

an input port and an output port;

a pair of wavelength self-shifting optical elements optically coupled between the input and output ports, the wavelength self-shifting optical elements being adapted to cause respective substantially equal and opposite wavelength changes of light traversing each element; and

a filtering element optically coupled between the frequency self-shifting optical elements, the filtering element being adapted to substantially reflect light of a selected wavelength, and substantially pass light of other wavelengths;

whereby light of a predetermined wavelength traveling in a forward direction between the input and output ports is shifted in wavelength away from the selected wavelength of the filtering element and thereby passes through the filtering element toward the output port, whereas light of the predetermined wavelength traveling in a reverse direction between the output port and the input port is shifted in wavelength to the selected wavelength of the filtering element and is thereby reflected back toward the output port.

8. A non-reciprocal optical element as claimed in claim 7, wherein said first and said second frequency self-shifting optical elements comprise nonlinear or strongly dispersive materials.

9. A non-reciprocal optical element as claimed in claim 7, wherein said filtering element is a Bragg grating.