Electro-optic Beam Research Articles

Integrated high-power electro-optic lens and large-angle deflector

We present a theoretical discussion and experimental demonstration of what to our knowledge is a novel integrated electro-optic lens and beam deflector fabricated in lithium tantalate. The cylindrical lens collimates Gaussian beams as small as 4 mum in diameter, whereas the independently controlled deflector is capable of scanning the collimated beam through an angular range of nearly 20 degrees .

Polymeric waveguide prism-based electro-optic beam deflector

Beam steering devices without moving parts are highly desir- able for their potential application in emerging optical technologies such as holographic optical storage systems, all optical networks, and optical switches. We demonstrate a thin-film waveguide beam deflector device that consists of an electro-optic prism array within a polymer waveguide. An electrode structure defines the prism array within the planar wave- guide. The deflection efficiency of 28 mrad/kV and the maximum deflec- tion angle of 68.4 mrad at 6300 V are obtained for this demonstration device. Further optimization of electrode-field poling and processing is likely to improve these results by at least an order of magnitude. © 2001

Improved output performance of high-power VCSELs

The intention of this paper is to report on state-of-the-art high-power vertical-cavity surface-emitting laser diodes (VCSELs), single devices as well as two-dimensional (2-D) arrays. Both approaches are studied in terms of electrooptical characteristics, beam performance, and scaling behavior. The maximum continuous wave (CW) output power at room temperature of large-area bottom-emitting devices with active diameters up to 320 /spl mu/m is as high as 0.89 W, which is to our knowledge the highest value reported for a single device. Measurements under pulsed conditions show more than 10-W optical peak output power. Also, the CW performance of 2-D arrays has been increased from 0.56 W for 23 elements to 1.55 W for 19 elements due to significantly improved heat sinking. The extracted power densities spatially averaged over the area close to the honeycomb-like array arrangement raised from 0.33 kW/cm/sup 2/ to 1.25 kW/cm/sup 2/. Lifetime measurements have proven acceptable reliability for over 10000 h at a degradation rate of less than 1% per 1000 h. The emission wavelength of bottom-emitting devices is restricted to about 900 nm or higher due to fundamental absorption in the GaAs substrate. Windowing of the substrate has been studied to allow for shorter wavelength emission.

Fabrication of electro-optic Pb(Zr, Ti)O3 heterostructure waveguides on Nb-doped SrTiO3 by solid-phase epitaxy

Pb(Zr, Ti)O 3 (PZT) heterostructure optical waveguides were grown on low resistivity Nb-doped SrTiO3(100) substrates by solid-phase epitaxy. The propagation loss was reduced to 1.7 dB/cm at the wavelength of 1.3 μm by introducing an epitaxial buffer layer between the PZT waveguide and the Nb-doped SrTiO3 substrate. An electro-optic beam deflector with an indium–tin–oxide prism electrode on the surface of the PZT waveguide showed efficient laser beam deflection as great as 3.3° (58 mrad) by applying 20 V between the prism electrode and the substrate. An index change higher than 0.001 at 5 V and an average apparent electro-optic coefficient larger than 46 pm/V were estimated from the deflection characteristic.

Shape-optimized electrooptic beam scanners: experiment

A new horn-shaped electrooptic scanner is described with significantly improved scanning sensitivity over rectangular-shaped devices. In the new device, the shape of the scanner is chosen to follow the trajectory of the beam. An example design is described that exhibits a factor of two larger scanning sensitivity than a rectangular device with comparable maximum scanning angle. Beam propagation simulations and measurements on an experimental device verify the scanner performance.

Integrated (Pb,La)(Zr,Ti)O3 Heterostructure Waveguide Devices Fabricated by Solid-Phase Epitaxy

AbstractHeterostructures of a Pb(Zr,Ti)O3 (PZT) waveguide/(Pb,La)(Zr,Ti)O3 (PLZT) system buffer layer were grown on a Nb-doped SrTiO3 (Nb:ST) substrate by solid-phase epitaxy. The propagation loss in the PLZT heterostructure waveguides was on the order of I dB/cm. An electro-optic beam deflection device with an ITO prism electrode on the surface of the PLZT heterostructure waveguide presented efficient deflection of the coupled laser beam by applying a voltage between the electrode and the substrate. A beam deflection greater than 10 mrad at 5 V and frequency response as fast as 13 MHz were observed. An apparent electro-optic coefficient as large as 39 pmJV was estimated from the deflection characteristics for the TE mode and TM mode suggesting the polarization independent nature of the PZT waveguide. For integrating the electrooptic PLZT heterostructure waveguides, channel waveguides were fabricated in the PZT waveguides using a simple wet-etching process. Based on a low-voltage drive structure, lowloss waveguide process, and fine patterning process, a fabricated digital matrix switch showed a – 10 dB cross-talk at a voltage as low as 7.5 V.

Shape-optimized electrooptic beam scanners: analysis, design, and simulation

This paper presents the analysis of a general nonrectangular electrooptic (EO) scanner and compare its performance to a rectangular device. Since the scanning sensitivity of an EO scanner is inversely proportional to its width, high sensitivity requires the device contour to be close to the ray trajectory of a beam propagating through the device. Accordingly, a shaped-optimized scanner is designed so that the beam trajectory at maximum deflection is parallel to the device contour. A beam propagation method (BPM) simulation shows the performance agrees well with the analysis.

Electro-optic beam deflector using epitaxial Pb(Zr,Ti)O3 waveguides on Nb-doped SrTiO3

Pb(Zr,Ti)O 3 (PZT) thin-film optical waveguides were grown on Nb-doped SrTiO3 substrates by solid-phase epitaxy to fabricate an electrode/waveguide/conductor structure. The propagation loss was relatively large for a PZT waveguide on a lightly Nb-doped SrTiO3 as compared with the propagation loss of 4 dB/cm for the structure using undoped SrTiO3. An electro-optic beam deflection device was fabricated by preparing a prism electrode on the surface of the PZT waveguide on a lightly Nb-doped SrTiO3 substrate. Efficient deflection of the coupled laser beam in the PZT waveguide as large as 11 mrad was observed by applying 35 V between the prism electrode and the substrate.

Electro-optic beam scanner in KTiOPO4

We have fabricated and demonstrated both wafer and waveguide electro-optic beam scanners in KTiOPO4 using alternating domain-inverted triangular patterns in the substrate. This device is an extension of previous work in LiTaO3. The domain inversion was achieved by pulsed electric field poling. The deflection sensitivity was 2.1 mrad/kV, compared to the calculated value of 2.3 mrad/kV for this geometry. The bandwidth of the devices was measured to be at least 200 kHz, which was limited by the high voltage driver.

Electrooptic wafer beam deflector in LiTaO/sub 3/

A novel electrooptic beam deflector is reported based on ferroelectric domain inversion extending through the thickness of a Z-cut LiTaO/sub 3/ wafer. The selective domain inversion is achieved by electric-field poling assisted by proton exchange, rather than proton exchange followed by rapid thermal annealing. The deflection sensitivity of the device was measured to be 5.0 mrad/KV. This is 93% of the theoretical value for this geometry, and a significant improvement over the value of 80% of theoretical previously reported for a waveguide deflector. This improvement is attributed to the new domain inversion process. No degradation of deflection sensitivity is observed up to the frequency of 300 KHz, which is then limited by the response time of detectors.

Potential and Current Distributions Calculated Across a Quantum Hall Effect Sample at Low and High Currents.

The potential and current distributions are calculated across the width of a quantum Hall effect sample for applied currents between 0 μA and 225 μA. For the first time, both a confining potential and a current-induced charge-redistribution potential are used. The confining potential has a parabolic shape, and the charge-redistribution potential is logarithmic. The solution for the sum of the two types of potentials is unique at each current, with no free parameters. For example, the charge-depletion width of the confining potential is determined from a localization experiment by Choi, Tsui, and Alavi, and the spatial extent of the conducting two-dimensional electron gas across the sample width is obtained from the maximum electric field deduced from a high-current breakdown experiment by Cage and Lavine, and from the quantum Hall voltage. The spatial extent has realistic cut-off values at the sample sides; e.g., no current flows within 55 magnetic lengths of the sides for currents less than 215 μA. The calculated potential distributions are in excellent agreement with contactless electro-optic effect laser beam measurements of Fontein et al.

Design and simulation of waveguide electrooptic beam deflectors

Numerical simulation based on the scalar beam propagation method, was used to investigate the performance of waveguide electrooptic beam deflectors. The deflectors under investigation consist of a stack of electrooptically controlled prisms in a waveguide. The results were compared to earlier simplified analysis. It was found that for given overall device dimensions, the number of interfaces between prisms in a prism-type electrooptic deflector has significant influence on the device performance when it is small. To avoid wavefront distortion, unwanted reflection from the interfaces, and asymmetry in the deflection angles caused by small number of interfaces, one should use more than about ten interfaces in a typical deflector. Additional insights of device operation and design issues are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Guided-wave electro-optic beam deflector using domain reversal in LiTaO/sub 3/

We have fabricated and demonstrated the operation of electro-optic beam deflectors using domain reversal in planar waveguides fabricated on LiTaO/sub 3/ substrates. The planar waveguides were made using proton exchange on z-cut substrates, and proton exchange with subsequent rapid thermal annealing was used to form the inverted domains. The deflection sensitivity of the device was measured to be about 6.7 mrad/kV. Calculations indicate that the deflection sensitivity should be increased by a factor of 25 to 30 with improvements in device geometry. >

Electro-optic beam deflectors for magneto-optic recording heads (abstract)

To make magneto-optic recording more competitive for data storage, the access times for the magneto-optic head must be reduced. By incorporating nonmechanical beam deflection into a split head architecture, fine access times can be reduced considerably and tracking robustness can be improved. Track switching times of ∼10 μs have been reported by Arimoto et al. using a surface acoustic wave beam deflector.1 In the present work, the use of electro-optic deflection techniques is discussed and demonstrated. Potential advantages of electro-optic scanners include lower power consumption and higher optical throughput. To demonstrate the use of an electro-optic beam deflector, an optical system using a commercially manufactured electro-optic deflector has been assembled to detect a signal from a magneto-optic sample. In this system, a 488 nm laser beam is sent through the deflector into a microscope which is used to focus the beam onto the medium. As the beam deflector scans a focused spot across a magnetic stripe domain on a thin film medium, the reflected beam is sent through a differential detection system which detects the change in polarization due to the Kerr effect. In this way, the presence of the domain is detected without mechanical motion. Experimental detection of 0.6 μm wide stripes has been demonstrated using this system. We believe similar beam deflectors in thin film form could significantly impact the performance of magneto-optic recording heads.

Electrooptic beam deflection using the leaky mode of a planar waveguide

Electrooptic beam deflection using the leaky mode of a TiO/sub 2/ thin-film waveguide in optical contact with a LiNbO/sub 3/ crystal is discussed. Initial measurements yielded a deflection efficiency of 0.34 mrad/kV and suggest potential for more than an order of magnitude improvement. By depositing the waveguide directly onto the electrooptical crystal, a rugged miniature device that has the potential for high-speed operation and an angular deflection efficiency equal to or higher than that of currently available bulk devices can be fabricated. In addition to the strict tolerances on the coating thickness, the deposited films must have extremely low losses, a high refractive index, and be resistant to environmental effects.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Subpicosecond reflective electro-optic sampling of electron-hole vertical transport in surface-space-charge fields

A new method of electro-optic sampling field transients, using above-band-gap optical probes in reflection, is analyzed theoretically and experimentally demonstrated to be within a factor of 2 as sensitive as electro-optic sampling in transmission. The technique is ideally suited to the study of interfaces due to the surface selective nature of the evanescent field probe. Studies of the dynamics of photogenerated electron-hole pair separation in surface-space-charge fields at GaAs(100)/oxide interfaces show that the hole carrier transit time is faster than 500 fs. Using longitudinal electro-optic sampling beam geometries, this technique has an intrinsic resolution of 50 fs.

Electrooptic beam deflection with latex

The use of latex in electrooptic devices is proposed. The static non linearity coefficient is shown to be approximatively 200 times the optical one. The theory of a beam deflector is developed and an explicit expression is given for the deflection angle versus the physical parameters of the sample Utilisation de suspensions aqueuses de latex dans un dispositif electro-optique. On montre que le coefficient statique de non-linearite devrait etre 200 fois plus eleve que le coefficient optique. Application a un deflecteur optique

A planar electrooptic beam splitter/modulator with a pair of parallel electrodes

A new planar electrooptic beam splitter with a pair of parallel electrodes is proposed and its characteristics are demonstrated on LiNbO3. At a voltage up to 80 V and a 9.5 μm electrode separation, the two output beams can be scanned over a total angle of 3° in the guide plane. The structure can also be applied to amplitude modulation, requiring 15 V for complete on-off modulation. The device permits convenient fabrication and has a potential to operate at high speeds.

Study of optical bistability and multistability with optical waveguide modulator

Using a planar optical waveguide electro-optic modulator and simple double beam interfering device, the experimental study of optical bistability and multistability is successfully performed. The waveguide modulator is made by depositing aluminium as electrodes on the Ti-diffused LiNbO2 planar optical waveguide which is fabricated by ourselves. Laser beam is coupled directly into the end of optical waveguide modulator and out of the Bi12GeO20 prism. Optical rotation arising from Bi12GeO20 crystal is overcome in experiment. In addition to analyzing and discussing optical bistability, the multistabilitical hysteresis curves of different shapes obtained in experiments are particularly investigated.

A Planar Electrooptic Beam Splitter with a Zig-Zag Electrode

A new planar electrooptic beam splitter with a zig-zag electrode is proposed, studied, and demonstrated. The device is simple in its electrode configuration, hence, it is easier to be fabricated and has a potential to operate at higher speeds. Theoretical analyses on a single element of electrodes, as well as on the array structure, have been carried out, and experimental devices have been realized on LiNbO/sub 3/ to demonstrate its characteristics. The experimental results show that the device has a deflection power two times greater than that of a beam splitter with conventional electrodes. In addition, an analysis of the incident angle of the optical beam onto the device shows that the device can be used as a pure beam splitter, a beam deflector, or a combination of the two.