Automated laser diode test system

• US 20020186744A1
• Filed: 05/14/2002
• Published: 12/12/2002
• Est. Priority Date: 05/14/2001
• Status: Active Grant

• Current Assignee: NeoPhotonics Corporation (Lumentum Holdings Inc.)
• Original Assignee: NeoPhotonics Corporation (Lumentum Holdings Inc.)
• Inventors: Walsh, John, Cornelius, Paul, Yim, Yong
• Granted Patent: US 6,873,172 B2
• Time in Patent Office: Days
• US Class Current: 372/109
• CPC Class Codes: H01S 5/0014 Measuring characteristics or properties thereof measuring techniques per se G01J, G01K, G01N, G01R
• CPC Class Codes: H01S 5/0021 Degradation or life time measurements
• CPC Class Codes: H01S 5/042 Electrical excitation ; Circuits therefor monolithically integrated laser drive components H01S5/0261

Abstract

An automated laser diode testing and burn-in system is disclosed. Initial device data is obtained by applying current to the device at room temperature and measuring the device parameters. The device is then subjected to a burn-in process at higher temperatures. Device performance is monitored throughout the burn-in process. Upon termination of the burn-in process the devices are cooled to room temperature and the post burn-in device power is measured again under the same test conditions. If the device parameters have changed by more than a particular amount the device is rejected. Otherwise, the device is accepted and installed in the next level assembly. The test system disclosed herein achieves significant advantages over prior art in cost and throughput by combining an easy to load laser test fixture with automatic device hold down feature, heating capability, computer program driven test protocol capable of performing initial laser measurements, calibrating each laser and photodetector pair, burn-in test, post burn-in measurements, failed device detection, storage of laser test history records and enabling remote access to such records. The invention eliminates the need for numerous labor intensive ergonomically difficult steps and costly test fixtures.

Claims

1. An automated laser testing system, comprising:

a heater assembly for holding lasers to be tester;

a detector assembly coupled to the heater assembly;

a burn-in fixture for receiving the heater and detector assemblies;

an electrical circuit for monitoring power level at the device being tested and adjusting the power as required; and

a module for identifying each heater assembly and retrieving a test plan.

2. The system of claim 1, wherein the module is a computer based test program.

3. The system of claim 1, wherein the module performs an initial test, auto calibration test, burn-in and post burn-in test of the lasers.

4. The system of claim 1, wherein the module applies pass and fail criteria, storing all data and capable of remote retrieval of stored data by a plurality of users.

5. The system of claim 1, wherein the heater assembly includes an electrostatic charge resistant base capable of elevated temperature applications.

6. The system of claim 5, wherein the heater assembly includes a laser holding device included with the heater assembly that is configured to receive and simultaneously release a plurality of lasers.

7. The system of claim 5, wherein the heater assembly includes a computer controlled heating and temperature control device disposed within the heater assembly and a computer readable heater assembly identification member.

8. The system of claim 1, wherein the detector assembly includes a photo detector and an integrating sphere for each laser being tested, the sphere being capable of receiving a reflective coating and collecting the light generated by the lasers.

9. The system of claim 8, wherein the detector assembly is configured to automatically determine a calibration set point for each laser,

10. The system of claim 9, wherein the detector assembly is configured to be detachably coupled to the heater assembly.

11. The system of claim 1, wherein the burn in fixture is capable of receiving the heater and detector assemblies, the burn in fixture configured to be loaded onto the burn in system.

12. The system of claim 11, wherein the burn in fixture further includes a movable handle, and a latching mechanism.

13. The system of claim 5, wherein the base is made of a polycarbonate material rated at 85 degrees Celsius or an ultem material rated at 120 degrees Celsius.

14. The system of claim 5, wherein the base is made of a material that is rate at 85 degrees Celsius or rated at 120 degrees Celsius.

15. The system of claim 5, wherein the base is made of electrostaticaly resistive material that is rated at least 80 degrees Celsius.

16. The system of claim 5, wherein the holding member is made of spring steel material.

17. The system of claim 5, wherein the heater assembly is controlled by a silicon integrated circuit transducer and an identification member that is parallel to a serial shift register device.

18. The system of claim 8, wherein the sphere includes a black polycarbonate or a lexan material.

19. The system of claim 18, wherein the sphere includes an additional coating.

20. The system of claim 19, wherein the additional coating is a titanium and gold coating.

21. The system of claim 1, wherein the electrical circuit comprises:

a transimpedance section for converting a photodetector current into a voltage signal; and

a switch member coupled to the transimpedance section, the switch member being capable of selecting between a constant current and constant power test conditions.

22. The system of claim 21, wherein the electrical circuit further includes an inverting operational amplifier coupled to the switch member, the inverting operational amplifier enabling a current flow in a desired direction.

23. The system of claim 22, wherein the electrical circuit further includes a summing junction positioned between the inverting operational amplifier and a circuit enable and disable switch.

24. The system of claim 23, wherein the electrical circuit further includes a controlling differential amplifier coupled to the summing junction, the controlling differential amplifier controlling current through the laser.

25. The system of claim 24, wherein the electrical circuit further includes a current boosting power transistor coupled to an output stage of the controlling operational amplifier.

26. The system of claim 25, wherein the electrical circuit further includes a differential operational amplifier coupled to the output stage of the controlling amplifier, the differential operational amplifier being configured to set a maximum laser current limit.

27. The system of claim 26, wherein the electrical circuit further includes a current sensing circuit for measuring current from the laser being tested, the circuit being coupled to the switch member and the laser being tested.

28. The system of claim 27, wherein the electrical circuit further includes a voltage monitoring buffer operational amplifier coupled to the current sensing circuit and the laser being tested.

29. The system of claim 28, wherein the electrical circuit further includes a tuning voltage supply operational amplifier coupled to a voltage divider operational amplifier, the voltage supply operational amplifier and the voltage divider being coupled to the laser tested and the differential amplifier to monitoring current leakage from the tuning voltage source, the voltage divider enabling storage of recorded data.

30. A method for testing lasers, comprising:

providing a browser user interface module to a server, providing a module enabling communications between the server, a parametric tester and an embedded controller; and

storing and retrieving test parameters and test data collected and enabling information retrieval by a plurality of local and remote users.

31. The method of claim 30, further comprising:

maintaining traceability of test data for each of a laser tested and to a specific location within a heater assembly.

32. The method of claim 31, further comprising:

detecting a location of a plurality of heater assemblies.

33. The method of claim 32, further comprising:

identifying each heater assembly.

34. The method of claim 30, further comprising:

recording a laser serial number for each of a tested laser.

35. The method of claim 30, further comprising:

performing a laser parametric test for each of a laser.

36. The method of claim 35, further comprising:

performing a calibration of each laser and a detector combination.

37. The method of claim 36, further comprising:

monitoring and adjusting a temperature of each of a laser tested to a predetermined value.

38. The method of claim 37, further comprising:

terminating a burn-in testing of each of a laser tested that does not conform to a predetermined value.

39. The method of claim 38, further comprising:

comparing a pre burn-in to a post burn-in a laser parametric test result; and

rejecting each of a tested laser when the laser parametric test result exceeds a predetermined value.

40. The method of claim 39, further comprising:

providing an embedded controller member for identifying each heater assembly; and

retrieving predetermined burn-in test conditions from the server.

41. The method of claim 40, further comprising:

continually monitoring temperature of lasers being tested;

42. The method of claim 41, further comprising:

providing a constant current or a constant power burn-in condition to lasers being tested.

43. The method of claim 42, further comprising:

measuring and adjusting test parameters to obtain constant power conditions for tested lasers.

44. The method of claim 43, further comprising:

storing laser test data and communicating the data to the server.

45. The method of claim 44, further comprising:

restarting a burn-in test if an interruption occurs during burn-in.

46. The method of claim 45, further comprising:

terminating the burn-in test and communicating the test termination message to the server.