Translume Writing With Lasers

Technology employs an ultrafast laser to write waveguides directly into an optical medium such as glass

October 11, 2001

2 Min Read

ANN ARBOR, Mich. -- Researchers at Translume have built an interferometric photonic device using their laser direct-write technology. Translume is located in Ann Arbor MI and concentrates on using laser direct-write technology to produce custom active and passive photonic components. Direct-write technology uses a focused beam from a femtosecond laser to change the index of refraction in a transparent dielectric. Because the light-dielectric interaction relies on a multi-photon process, the index change is localized to a small region around the focus where the beam intensity is highest. By scanning the beam through the material, a path of altered refractive index can be created that acts as a waveguide. Direct-write technology has several advantages over conventional planar technology. It is possible to create three dimensional optical circuits which can reduce the footprint of existing circuit designs, allow more complicated circuit designs, and makes it easier to interface arrays of taps to detector arrays. Direct-write technology does not require a clean room environment or mask production, making it inherently cheaper and quicker for producing smaller batches of components and custom designs. Also, because the waveguides are not produced in a vacuum chamber, production , testing and even correction (trimming) can all occur without ever having to transfer the device. This makes the technology competitive even for large scale manufacturing of high-accuracy interferometric devices. The prototype device is an interleaver (an unbalanced Mach-Zhender interferometer) which are typically used in WDM systems to separate adjacent wavelength channels. It consists of two (approximately) 50:50 directional couplers whose arms are connected by two waveguides that differ in length by 500 um, corresponding to a channel spacing of 400 GHz. The entire device was created by scanning a beam of 120-fs, 100-nJ pulses from a Ti:Sapphire laser perpendicular to the beam's propagation direction. It is contained in a 1x5 cm area, 300 um below the surface of a glass block. At 800 nm the waveguides exhibit a mode field diameter of 5 um and are polarization maintaining. The contrast between adjacent channels is 10 dB. The device was designed to operate at a wavelength of 800 nm but extension to telecom wavelengths is straightforward since waveguides have been written that work out to wavelengths longer than 1600 nm. Current work includes developing the process to produce devices with much higher specifications and using slightly modified device designs to produce photonic switches. Translume Inc.

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