The integrated optics section describes the overall method for creating integrated optical circuits in volume photopolymers. This section describes in more detail work that we have done on writing waveguides in the photopolymer.
A laser of a wavelength that initiates polymerization is tightly focused into the bulk of a photopolymer sample, and the sample is translated either perpendicular or parallel to the propagation of the writing beam, creating a line of index change in the material as shown in the figure below.
This method is similar to that used for writing index features in glass with a femtosecond laser. Unlike femtosecond writing in glass,
in which the index change is a strongly nonlinear function of intensity, the
photopolymer responds with an index change nearly proportional to the time
integral of the writing intensity, creating gradient index structures that
resemble the intensity profile of the writing beam. The index structures are
thus confined in depth in the polymer, and so this method can be used to write
arbitrary 3D index structures with minimum feature sizes given by the scale of
the writing focus. We have been able to demonstrate single mode waveguides at 633 nm using only ~ 30 μW or incident writing light.
We are currently investigating the response of these photopolymers to the high intensity beams used for writing. The method used to characterize the waveguides and thus the response of the materials is described in the tomography section of this website.
While other group members are concentrating on material modeling, perpendicular waveguide writing, waveguide arrays and optical interconnects, I have focused most recently on optimizing parallel written waveguides. Since the index created in the polymer is dependent on both the intensity profile of the writing beam and the time that the beam is incident upon the material, by varying the writing parameters such as power, speed of sample and material absorption, we can create waveguides that taper along their length. Tapered waveguides are valuable for connecting modes of different sizes and shapes.
We are currently investigating the response of these photopolymers to the high intensity beams used for writing. The method used to characterize the waveguides and thus the response of the materials is described in the tomography section of this website.
While other group members are concentrating on material modeling, perpendicular waveguide writing, waveguide arrays and optical interconnects, I have focused most recently on optimizing parallel written waveguides. Since the index created in the polymer is dependent on both the intensity profile of the writing beam and the time that the beam is incident upon the material, by varying the writing parameters such as power, speed of sample and material absorption, we can create waveguides that taper along their length. Tapered waveguides are valuable for connecting modes of different sizes and shapes.