1300nm Beam Profiling - InGaAs vs Standard CCD Camera
A manufacturer needed to profile and measure diodes that produce a 1300nm CW source in the 10's of mW's. The inspection needed to be conducted in seconds with full accuracy and repeatability because100% inspection was specified to insure the quality level needed by the customer. As this component was a basic element to the finished product, if any defects could be identified at this stage, a significant savings in scrap product would be realized vs attempting to rework finished product.
The initial solution offered by Ophir-Spiricon was the standard silicon array, BGP-USB-SP503 camera, operating BeamGage® Professional software. This camera offers a large array (6.3mm x 4.7mm) with 9.9μm square pixels (640x480). The silicon array is specified for use from .190um to 1.1um.
Experience has shown that with sufficient average power, the silicon array is suitable for 1.3um as well. The original specification shows:
Figure 2. Original SP503 camera specification.
However, in a more recent revision, the Spiricon engineers reduced the sensitivity to a range of .190um to 1.1 (although, when sufficient power exists, it can still be used at 1300nm).
Figure 3. Current SP503 camera specification.
Spiricon engineers noted, “Although our silicon array cameras have shown response out to 1.32um, it can cause significant blooming which could lead to significant errors of beam width measurements.”
For this diode application the source was 1300nm. This is typically suitable for this camera with the risk of blooming, as seen below:
Figure 4. Blooming can lead to errors in beam width measurements.
Cost Differential: Standard CCD Camera vs InGaAs Camera
Due to the competitive nature of this customer’s business, it was necessary to test the lower cost, standard silica CCD camera first. The risk of blooming was likely, but it was possible they could compensate for this phenomenon. The SP503 standard CCD camera was fixtured and, using BeamGage Professional software, the data was fed into the data analysis system for the quality evaluation. This proved to be useable but did not present the needed accuracy. A typical 1300nm beam image with the standard CCD silica array camera had this appearance:
Figure 5. Typical 1300nm beam with standard CCD silica array camera.
As a test for comparison, the Ophir-Spiricon InGaAs camera was suggested as a better alternative. It would not be affected by the blooming condition and provided further confidence the sensitivity of the array was well suited for this wavelength (Spiricon InGaAs camera specified for 0.90-1.7um, with 30um x 30um pixels, 320x256). This camera was also programmed with BeamGage Professional software and then tested and compared against the standard CCD array camera.
Figure 6. InGaAs camera.
The test results proved quite satisfactory. A typical beam profile of the same diode showed the following image:
Figure 6. InGaAs camera.
The cost differential of the Ophir-Spiricon InGaAs camera, which is quoted at 4x the cost of the standard CCD camera, was easily justified by the accuracy this camera could offer, the reliability in measurement it provided, and the reduced scrap this alternative would produce in the manufacturing process.