GePSG core for a planar lightwave circuit

• US 6,615,615 B2
• Filed: 06/29/2001
• Issued: 09/09/2003
• Est. Priority Date: 06/29/2001
• Status: Expired due to Term

• Current Assignee: NeoPhotonics Corporation (Lumentum Holdings Inc.)
• Original Assignee: Lightwave Microsystems Corporation (Lumentum Holdings Inc.)
• Inventors: Zhong, Fan, Bornstein, Jonathan G.
• Primary Examiner(s): Lee, John D.
• Assistant Examiner(s): Doan, Jennifer
• Application Number:
  US09/895,583
• Publication Number:
  US 20030002836A1
• Time in Patent Office: 802 Days
• Field of Search: 385/129, 385/130, 385/131, 385/132, 654/13, 654/14, 654/15, 654/16, 654/17, 654/18, 654/19, 654/20, 654/21, 654/22, 654/23
• US Class Current: 65/413
• CPC Class Codes: G02B 2006/12169 Annealing
• CPC Class Codes: G02B 6/105 having optical polarisation effects
• CPC Class Codes: G02B 6/12023 characterised by means for reducing the polarisation dependence, e.g. reduced birefringence
• CPC Class Codes: G02B 6/122 Basic optical elements, e.g. light-guiding paths
• CPC Class Codes: G02B 6/132 by deposition of thin films

Abstract

A method of depositing a core layer for an optical waveguide structure of a planar lightwave circuit. A GePSG core for an optical waveguide structure of a planar lightwave circuit is fabricated such that the optical core comprises doped silica glass, wherein the dopant includes Ge and P. In depositing a core layer from which the optical core is formed, two separate doping gasses (e.g., GeH₄ and PH₃) are added during the PECVD process to make Ge and P doped silica glass (GePSG). The ratio of the Ge dopant and the P dopant is configured to maintain a constant refractive index within the core layer across an anneal temperature range and to reduce a formation of bubbles within the core layer. The ratio of the Ge dopant and the P dopant is also configured to reduce refractive index birefringence within the core layer across an anneal temperature range.

Claims

1. A method of depositing a core layer for an optical waveguide structure of a planar lightwave circuit, the method comprising the steps of:

a) providing a flow rate for a Ge dopant for a SiO₂ core layer deposition;

b) providing a flow rate for a P dopant for the core layer deposition; and

c) controlling the flow rate for the Ge dopant and the flow rate for the P dopant to form the core layer, thereby increasing refractive index stability of the core layer across an anneal temperature range, and wherein the controlling of the flow rate for the Ge dopant and the flow rate for the P dopant is configured to reduce a formation of bubbles within the core layer.

2. The method of claim 1, wherein the controlling of the flow rate for the Ge dopant and the flow rate for the P dopant is configured to increase refractive index stability of the core layer across an anneal temperature range from 900 C. to 1200 C.

3. The method of claim 1, wherein the controlling of the flow rate for the Ge dopant and the flow rate for the P dopant is configured to reduce birefringence within the core layer across an anneal temperature range for the core layer.

4. The method of claim 1, wherein the Ge dopant comprises GeH₄, Ge₂H₆ or Ge(C₂H₅O)₄.

5. The method of claim 1, wherein the P dopant comprises PH₃ or tetramethyl phosphine (TMP).

6. The method of claim 1, further including the step of using a thermal anneal process with a temperature in a range of 900 C. to 1200 C. after the core layer deposition of step c).

7. A method of depositing a core layer having a reduced birefringence for an arrayed waveguide grating device, the method comprising the steps of:

a) providing a flow rate for a Ge dopant for an SiO₂ core layer deposition;

b) providing a flow rate for a P dopant for the core layer deposition; and

c) controlling the flow rate for the Ge dopant arid the flow rate for the P dopant to form the core layer, thereby reducing birefringence within the core layer, wherein the controlling of the flow rate for the Ge dopant and the flow rate for the P dopant is configured to reduce a formation of bubbles within the core layer during an anneal process.

8. The method of claim 7, wherein the Ge dopant comprises GeO₂.

9. The method of claim 7 wherein the controlling of the flow rate for the Ge dopant and the flow rate for the P dopant is configured to reduce a center wavelength shift of the arrayed waveguide grating device.

10. The method of claim 7, further including the step of using a thermal anneal process with a temperature in a range of 900 C. to 1200 C. after the core layer deposition of step c).

11. The method of claim 7, wherein the controlling of the flow rate for the Ge dopant and the flow rate for the P dopant is configured to reduce birefringence within the core layer by tuning a CTE within the core layer.

12. The method of claim 7, wherein the controlling of the flow rate for the Ge dopant and the flow rate for the P dopant is configured to control the width of the waveguide core.

13. A method of depositing a core layer for an optical waveguide structure of a planar lightwave circuit, the method comprising:

flowing a Ge dopant for a SiO₂ core layer deposition;

flowing a P dopant for the core layer deposition; and

controlling a flow rate for the Ge dopant and a flow rate for the P dopant to form the core layer, wherein the controlling of the flow rate for the Ge dopant and the flow rate for the P dopant is configured to reduce a formation of bubbles within the core layer.

14. The method of claim 13, wherein the controlling of the flow rate for the Ge dopant and the flow rate for the P dopant is configured to increase refractive index stability of the core layer across an anneal temperature range from 900 C. to 1200 C.

15. The method of claim 13, wherein the controlling of the flow rate for the Ge dopant and the flow rate for the P dopant is configured to reduce birefringence within the core layer across an anneal temperature range for the core layer.

16. The method of claim 13, wherein the Ge dopant comprises GeH₄, Ge₂H₆ or Ge(C₂H₅O)₄.

17. The method of claim 13, wherein the P dopant comprises PH₃ or tetramethyl phosphine (TMP).