I have a bulk quasi-phase matched non-linear crystal with waveguide dimension of 5um*4.5um, as provide in this link http://www.hcphotonics.com/products2.asp?area=1670&cat=1751&sn=938.
Is there any easy experimental scheme to couple laser light into such bulk crystal? we are currently focusing laser light onto the front facet of the waveguide, and collimate it with another lens, the waveguide is mounted on a xyz positioner with 10um micrometer precision.
I have an idea of using SNOM tip? as the beam diameter can then be brought down to 50nm. Update: I found some coupling tutorial on the internet, apparently the method we are using is called Direct focusing. this is the simplest scheme yet most stringent on the condition of alignment.
Dear James,
For free space coupling you might choose the objective lens to focus the beam into diameter around 4um. With a 3 axis translation stage you can optimize the lateral and longitudianl postion. However, 10um precision might be a little rough to the waveguide since the mode field is only 6x3um (it should be fine).
Thanks Cheng. It couples very well now, however we now face the problem of spectral broadening due to the ultrashort pulse inside single mode fiber.
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