A very high energy Q-switched Er-glass laser is reported. We incorporated a rotating, resonant mirror/Porro-cavity reflector optical arrangement to achieve very high shutter speeds on the cavity Q of a laser designed for energetic, flashlamp-pumped, 600-μs, 1540-nm pulses. Reproducible 3.75-J, 35-ns, 1533-nm laser pulses were obtained at a repetition rate less than 1 minute. Our work shows that reliable, very high energy, Q-switched, Er-glass laser pulses at 1533 nm can be generated mechanically with no apparent damage to laser cavity components. We demonstrate the applications of this "eye safe" wavelength to energetic processes such as LIBS and materials processing. The laser could also serve as a new tool for bioeffects studies and targeting applications.
We fabricated and demonstrated a beam deflector implemented in an electro-optic polymer planar waveguide. An array of prism- shaped electrodes formed on the top of the waveguide induces selective refractive index change in the core polymer layer, which results in the tilt of the propagation direction of the guided beam. Waveguide beam deflectors have potential applications in the emerging photonics technologies such as optical storage systems, optical phased array antenna, and optical switching. The deflection sensitivity of 28 mrad/kV, and the maximum deflection angle of +/- 8.4 mrad at +/- 300 V were obtained for this first demonstrated device.
In this paper, we demonstrate a thin-film polymeric waveguide beam deflector using a new device concept, an electrode of prism-array pattern on top of a three-layer planar waveguide. The three-layer planar waveguide was composed of UV15 as the top cladding layer, a polyimide as the core layer, and SiO<SUB>2</SUB> as the bottom cladding layer on a silicon substrate. A gold layer was deposited on the top of the waveguide by e-beam deposition and then patterned into a prism-array as the heating electrode by photolithography.
A novel approach for laser beam deflection using the thermal optic prism array in a polymeric planar waveguide is developed. This approach is based on the different thermo- optic properties between polymer and silica, the two optical materials employed for the guided wave beam deflector. A waveguide structure with the core layer composed of inversely positioned polymer and silica triangles forming a polymer/silica prism array has been fabricated. Through electrical heating, a temperature change results in an index difference between the two optical materials and creates an optical prism structure in the polymer/silica planar waveguide. A beam deflection of 5.4 degree was observed under a temperature change of 60 degrees C in the fabricated prism array. The sensitivity of the device is 0.09 degrees/degrees C. A maximal number of resolvable spots of 8 was achieved at a low driving power from the thermo-optic prism array structure. The accuracy of beam deflection approaches 16 micro-radian. The device fabricated has a thickness of 5 microns, a prism aperture width of 600 microns, and a device length of 7 mm. Optimal design to maximize the deflection angle and the number of resolvable spots has been evaluated.
CMOS compatible optical polyimide based thermo-optic switches have the potential use as low-power switches. These switches would have many advantages over other switches based on inorganic crystals. For one, they can be integrated into module-to-module systems using currently available VLSI fabrication techniques. Polyimide based, 1 by 2 thermo-optic switches are fabricated onto silicon wafers and tested. We report the properties and characteristics of digital thermo- optic switches designed to operate at 1.3 micrometers . Also, the switching characteristics at different heating electrode voltages are tested and compared.
This paper reports our efforts to develop an optical True- Time-Delay line module for Phased Array Antenna applications using optical polymeric waveguides. We first give a brief description of a targeted phased array antenna, having chosen a 16-element sub-array as our demonstration system. Then we address the design considerations of the True-Time- Delay lines pattern based on the sub-array antenna's parameters, including simulations we have done to optimize the building blocks of the pattern: splitters, arcs' curvature, and crossings. Finally, we describe the steps of a modified fabrication process and present the primary result. Our experiment shows that the polyimide-based waveguide has a promising future because it has high fabrication precision and packaging density.
We have demonstrated a polymeric electro-optic modulator based on a 1 X 2 Y-fed directional waveguide coupler. The symmetric geometry of the 1 X 2 Y-fed directional coupler provided the modulator unique characteristics of intrinsic 3 dB operating point and two complementary output ends. A low switching voltage of 3.6 V and a high extinction ratio of 26 dB were obtained with the modulator operating at a wavelength of 1.34 micrometers . The modulator was fabricated with a novel electro-optic polymer that was synthesized from polyurethane crosslinking with a chromophore.
A beam deflector device has been demonstrated that used thin-film electro-optical polymeric waveguide. Prism cascade was fabricated within a planar waveguide. We report the detail of the design and fabrication of new polymer material beam deflector to operate at 1.3 micrometers .
We present an innovative approach for fabricating a polarization modulator, which outputs light alternating in time between left- and right-hand circular. The aim is to replace bulky and expensive photoelastic, liquid-crystal, or inorganic-crystal polarization modulators for certain applications. We use a single-mode polymer waveguide, where a controllable amount of birefringence via the electro-optic effect adjusts the output polarization. It has a very small mass, low power consumption, and very compact size. Other desirable attributes are its use of no moving parts, low voltages, and a single high-speed voltage source. The wavelength of operation is adjustable from 700 to 1600 nm. Furthermore, it can operate at arbitrary frequencies up to the GHz range as compared to the KhZ operating frequencies of photoelastic and liquid-crystal modulators. We show how to overcome the problem of different TE an TM mode amplitudes in polymer waveguides and how to ease the fabrication and packaging tolerances. We present some performance data on a polymer waveguide that outputs circularly polarized light.
Polymer thermooptic waveguide taps have a potential application as light routers for guided wave optical interconnects involving cascaded fanouts. The taps can guide light form an optical bus bar and direct it into other devices in a switching/modulation network. Thermooptic waveguide taps are designed and fabricated on silicon wafers using standard VLSI fabrication techniques. Coupling of light into an adjacent waveguide tap is observed to increase by 12.3 percent from 38.7 percent to 51.0 percent with the application of 34 mW of power.
We report the demonstration of a compact laser-beam deflector based on electro-optic prisms formed within a thin-film polymer waveguide. We fabricate planar waveguides using a polymer that can be readily poled and cured through the simultaneous application of a poling voltage and heat. The index of refraction of each prism in the cascade, but not of the surrounding polymer, is modulated by the electro- optic effect through the application of a drive voltage. A laser beam, to be deflected, is coupled into and out of the planar waveguide by cylindrical lenses. The application of a drive voltage creates a sequence of prisms in the planar waveguide, which change the path of propagation of beam through the planar waveguide with a variable angle of refraction depending upon the voltage. The deflection efficiency is observed to be nearly 100 percent and the laser beam maintains its Gaussian intensity profile after propagating through the device.
Electrooptic polymer-based modulators have been investigated intensively due to their potential applications in optical communication systems. In this paper, we report a polymeric modulator with a domain-inverted Y-coupler configuration. Both of the modulation depth and linearity were improved due to the novel device structure. The Y-coupler modulator was automatically set at 3dB point with no need of DC bias, which eliminate the DC drift phenomena in Mach-Zehnder or co-direcitonal modulators. At the same time, a domain- inversion poling technique was developed, which can be used to fabricate other type of active EO devices in the future.
A beam deflector has been designed and fabricated that uses a nonlinear-optical polymer. The device is composed of a cascade of polymeric electro-optic prisms formed within a planar waveguide of the same polymer system. A laser beam, to be deflected, is coupled into and out of the planar waveguide by cylindrical lenses. The light path of the laser beam within the planar waveguide is adjusted to pass through the successive prisms of the cascade, where the Gaussian transverse-mode profile is centered (initially) within each of the prisms. The index of refraction of each prism in the cascade, but not of the surrounding polymer, is modified by the electro-optic effect when a drive voltage is then applied. The application of a drive voltage thus causes the planar waveguide to function as a sequence of prisms that change the path of propagation of the beam through the planar waveguide. The collimated beam formed by the output cylindrical lens deflects. The extent of deflection is proportional to the amount of refractive-index change induced in the prism cascade. A uniform electrode structure can drive the electro- optic prism cascade, which should enable the device to operate at high speeds when traveling-wave driven.
We use high temperature liquid-contact poling as a method to pole efficiently cladded nonlinear optical polymer films. Poling voltage as high as 400 volts is applied to planar waveguides which have a nonlinear optical film of 1.2 im thick. The lack of a quick method to characterize the poled cladded nonlinear optical films inspires us to devise a new electrooptic measurement method. This method can determine r33 and r13 separately because it uses light of single polarization state to probe the nonlinear optical film. The interference between the modulated light and the unmodulated light in the reflected beam is used to extract electro-optic coefficients. Theoretical analysis of the relationship between the reflected light intensity and the electro-optically modulated signal is consistent with the experimental results. Formulae to calculate electro-optic
coefficients are deduced. This method uses an even simpler experimental setup than that of the widely used ellipsometric
LD-3 polymer directional couplers have the potential use as low-voltage modulators and switches. They can be integrated into module-to-module systems using currently available VLSI fabrication techniques. Modes of channel waveguides are calculated and coupling lengths are determined using BPM_CAD. We report the fabrication of LD-3 polymer directional couplers designed to operate at 1.3 micrometers .
Crosslinked polymers offer the promise of great long term temporal stability and chemical resistance. However, a crosslinkable nonlinear optical (NLO) polymer is more difficult to be processed into high optical quality thin films than other type of NLO polymers such as side-chain, main-chain or guest-host polymers. The crosslinking process imposes more stringent requirements on the solvents. The process of searching for a compatible solvent for a crosslinkable NLO polymer is described. Two detrimental phenomena during the fabrication of electrooptic waveguides from crosslinkable polymers are reported. One is the crystallization of the crosslinker. The other is the formation of wavy surfaces when a commercially available optical adhesive is used to prepare the cladding. By anchoring the small molecules to the long chain NLO polymer and precuring the optical adhesive, good optical quality polymer waveguides are prepared.
Directional couplers with four sections poled in four perpendicular directions are proposed for the first time as a new electro-optic switch configuration in which complete conversion of both TE and TM light from one waveguide to the other can be achieved simultaneously by a low driving voltage adjustment. The perpendicularly poled sections of the switch make the device completely polarization- independent, and the inversely poled sections offer an extremely relaxed fabrication tolerance for the device. This configuration of each section poled in a different direction also makes it possible to drive the electro-optic coupler with a uniform electrode, which ensures high-speed operation of the device. Both the switching characteristics and the fabrication tolerance are simulated.
Domain-inverted electro-optic films have many applications in photonic devices such as high-speed electro-optic switches and quasi-phase-matched second-harmonic generators. For example, inverted domains allow a uniform electrode structure to be used in a reversed-(Delta) (beta) directional coupler. Since corona poling is not applicable to create inversely poled structures in a crosslinkable polymer, direct-contact poling and liquid-contact poling are investigated. In unidirectional poling, liquid-contact poling allows poling electric fields higher than 250 V/micrometer to be applied, which is comparable to electricfield strengths in corona poling but much higher than those in direct-contact poling. For domain-inversion, the results also show that liquid-contact poling allows much higher poling electric fields to be applied than in direct- contact poling.