ATHERMAL BIREFRINGENT FILTERS

 

Thermal Compensation Technology
We have recently developed the capability to design and produce passive telecom components based on birefringent materials. One of the most critical requirements for de-interleavers and demultiplexers (and other passive filtering components) is frequency stability over the required 0 to 70°C operating range. Our athermal filter designs utilize a dual-crystal approach where a second crystal is used to compensate the temperature drift of a first wavelength-filtering crystal. The graph shown below is an example of the thermal stability that can be achieved by using our approach.
In the graph shown above, the wavelength drift of a single YVO4 filtering element over the 24 to 67°C temperature range without (purple) and, over the 12-105°C temperature range, with (blue) a second temperature-compensating birefringent crystal. In addition, we have developed temperature-compensation methods for other birefringent materials such as TeO2. For customers that have already designed their own components based on birefringent materials, we can supply temperature-compensated wavelength-filtering crystal pairs in both prototype and production quantity.


Passive Component Prototypes
Our athermal birefringent filters, which consist of temperature-compensated crystal pairs for wavelength filtering, can be used to create a wide variety of passive telecom components including:

-interleavers
-gain-flattening filters
-dispersion compensators
-multiplexers/demultiplexers

Since we have in-house crystal growth, optical fabrication, and a machine shop, we can rapidly produce passive component prototypes to meet each customer's unique specifications. The PDF-format Isomet Demultiplexer white paper provides a complete description of our 100-GHz demultiplexer/de-interleaver. We have recently redesigned our Isomet Demultiplexer to further reduce cost and complexity; click here for the datasheet on the new Isomet Interleaver.

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