A new compact optical circulator based on a photonic crystal made of a triangular lattice of air holes etched in a magneto-optical material that does not require an external DC magnetic field to keep its saturated magnetic state is presented. The design has a threefold rotational symmetry and it consists of three single-mode waveguides and one resonator supporting dipole resonances introduced in the photonic crystal structure. Computational simulations of the circulator demonstrate that, at the 1.55 µm wavelength, the insertion losses are about -1 dB, while the isolation and reflection levels are about -15 dB and -24 dB, respectively.
We present a study of polarization rotation enhancement in birefringent magneto-optic photonic crystal waveguides
and provide theoretical and experimental support for a novel type of photonic bandgap. The coupling
between counter-propagating elliptically birefringent local normal modes of different order results in the formation
of partially overlapping bandgaps and selective suppression of Bloch state propagation near the band edges.
We use a bilayer unit cell stack model with an alternating system of birefringent states in adjacent layers. A
magnetically tunable and large polarization rotation of the allowed Bloch modes near the band edges is computed
theoretically and observed experimentally.
By trapping photons in fabricated phase-shift defects magnetic photonic crystals can enhance the Faraday rotation in magneto-optic films. The integration of these structures into on-chip photonic circuits, while advantageous from the point of view of component connectivity in multi-functional systems, faces several challenges. Differences in effective refractive indices between transverse electric (TE) and transverse magnetic (TM) modes engender phase disparities, thus hindering the Faraday response of the material. Moreover, photonic waveguide structures in magnetic films may support more than one mode depending on the waveguide thickness and refractive index. The effects of birefringence and multimodality on the performance of waveguide magnetic photonic crystals in magnetic garnets are discussed in paper. Particular attention is paid to analyzing the effect of Faraday rotation enhancement in magnetophotonic crystals in the presence of waveguide birefringence and modal multiplicity. Multiple stopbands and significant polarization rotation are observed in multimode Bi-substituted iron garnet film waveguides with single-defect photonic crystal structures. A spectrally flat response is predicted for the polarization rotation in first order mode for birefringent waveguides. The photonic crystals for this study are patterned on ridge waveguide films by focused ion beam (FIB) milling.
A smart cantilever structure using single-crystal relaxor ferroelectric material is presented. The smart cantilever possesses both sensing and actuation capabilities, embedded in a monomorph and resulting in a smart structure. Single crystal relaxor ferroelectric materials (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-PT) and (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) are ideal for actuator and sensor applications since they exhibit very high piezoelectric coefficients. We separately pattern interdigitated electrodes on the top and bottom surfaces of a single crystal cantilever beam. The interdigitated electrode design results in an electric field- gradient that after poling not only induces flapping actuation but also, simultaneously, allows us to detect internally or externally induced stresses. As a monolithic actuator integrated with a sensor, it has potential applications in various Micro-Electro-Mechanical Systems (MEMS), Scanning Probe Microscopy (SPM) and Near-field Scanning Optical Microscopy (NSOM). We fabricate monomorph prototypes and characterize their performance in terms of actuation displacement and sensing capabilities, respectively. Finally, an active vibration control experiment was successfully conducted by using the smart cantilever structure.
In this paper, novel piezoelectric microbalance biosensors using single crystal lead zinc niobate-lead titanate (PZN-PT) and lead magnesium niobate-lead titanate (PMN-PT) are presented. The PZN-PT/ PMN-PT materials exhibit extremely high piezoelectric coefficients and other desirable properties for biosensors, supposed to be a superior substitution for the conventional quartz crystal with the improved performance. . These biosensors provide rapid and minute quantitative target detection by monitoring the change in resonance frequency of the crystal probe. With the geometrical variations, various prototypes are compared with conventional quartz crystal microbalances (QCM). The superiority of the materials over conventional quartz crystal is demonstrated experimentally in terms of sensitivity. In addition, we examine the feasibility of ultra miniaturization of the PZN-PT based biosensor by fabricating freestanding single crystal films of the PZN-PT and patterning micro-scale biosensors with ion milling and argon-ion laser-induced etching technique. A fabricated prototype sensor utilizing the material in a thin film form has a size of 300x100x7um3.
Miniaturized on-chip optical isolators are highly desirable for advanced optical telecommunications to eliminate noise and protect the laser source. This talk will discuss the fabrication and testing of on-chip photonic crystals in ferrite waveguides. Photonic band gap engineering can produce Faraday rotators with highly enhanced polarization rotation for ultra-small integrated optical isolators. The main challenges to such devices are the elimination of linear birefringence and the efficient production of planar photonic band gap nanostructures. These challenges are addressed in the present article. In particular, we demonstrate the presence of stopbands and resonant polarization response in single-defect magneto-optic photonic crystal waveguides. However, waveguide birefringence degrades the magneto-optic response and results in significant ellipticity at resonance. Lower birefringence waveguides are required for enhanced magneto-optic performance.
This paper presents an investigation of a stand-alone PZN-PT film-based movable micro-mirror and characterizes its precision level. Micro-mirrors have received considerable attention for applications in various micro-opto-electro-mechanical systems (MOEMS). For example, there is considerable interest in creating micro-mirror arrays for image display and telecommunication applications. Such optical applications require high precision position control of micro-mirrors. We present the development of stand-alone self-moving micro-mirrors on the basis of a single-film actuation mechanism. The mirror design provides for tilt motion using a single-crystal Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) film unimorph actuator. A prototype micro-mirror plate is designed to a size of 600 × 400 × 10 μm3 including actuation device. In this paper, it is shown that a prototype micro-mirror fabricated in our laboratories can be operated at frequency of 50 kHz.
In this paper we will review our efforts in developing both design and fabrication capabilities for photonic integrated circuits. Design is based on software for CAD and beam propagation simulation of planar waveguide circuits. Fabrication is based on a laser-based rapid prototyping system for patterning and processing waveguide materials.
In this paper, we will describe our work at Columbia in developing a laser prototyping system, in conjunction with computer simulation, to design, fabricate, and test novel waveguide circuits. The system is also useful for manufacturing small-run circuit designs. The fundamental technique uses a laser-induced photoelectrochemical process for etching GaAs and other III-V compounds. The technique is maskless and discretionary. The computer-controlled apparatus can be programmed with any desired circuit pattern, and prototype waveguide circuits can be produced within a day. The waveguides and passive components produced with this technique include linear waveguides, tapered waveguides, abrupt and smoothly curved bends, Y-branches, asymmetric splitters, directional couplers, and optical delay lines. The passive devices are single-mode and low-loss. The technique also has the ability to vary the effective index of refraction along the device by grading the etch depth. In addition to passive devices, we have recently shown that active switching components can be prototyped by combining passive structures with laser-patterned metal electrodes. These electrodes are produced masklessly using standard metal deposition techniques coupled with laser- patterning of photoresist. In addition, metal can be deposited directly using laser-induced selective metallorgainic CVD.