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Title: Fabrication and characterizations of proton-exchanged LiNbO{sub 3} waveguides fabricated by inductively coupled plasma technique

Abstract

This Letter reports the use of an inductively coupled plasma technique for fabrication of proton-exchanged (PE) LiNbO{sub 3} (LN) waveguides. Planar and stripe waveguides have been formed in Y-cut LN which are difficult to obtain with the conventional molten acid method due to the occurrence of surface damage. Secondary ion mass spectrometry, scanning electron microscopy, and infrared absorption spectrum characterization results revealed that a uniform vertical PE profile with a single low order crystal phase has been directly obtained as a result of this unique process. X-ray photoelectron spectroscopy characterization of the treated surface revealed the existence of NbO as the cause for a sometimes darkened surface and confirms the ability to completely restore the surface to LN by oxygen plasma treatment. Atomic force microscopy measurement confirms that good surface quality has been maintained after regeneration of the surface to LN.

Authors:
; ; ; ; ; ;  [1];  [2];  [2];  [2];  [2];  [2]
  1. Department of Electrical and Electronic Engineering, University of Bristol, Bristol BS8 1UB (United Kingdom)
  2. (United Kingdom)
Publication Date:
OSTI Identifier:
20779166
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 88; Journal Issue: 14; Other Information: DOI: 10.1063/1.2191704; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ABSORPTION SPECTRA; ATOMIC FORCE MICROSCOPY; CRYSTALS; FABRICATION; INFRARED SPECTRA; ION EXCHANGE; ION MICROPROBE ANALYSIS; LITHIUM COMPOUNDS; MASS SPECTRA; MASS SPECTROSCOPY; NIOBATES; PLASMA; PROTONS; REGENERATION; SCANNING ELECTRON MICROSCOPY; WAVEGUIDES; X-RAY PHOTOELECTRON SPECTROSCOPY

Citation Formats

Ren, Z., Heard, P.J., Hallam, K.R., Wotherspoon, Alex, Jiang, Q., Varrazza, R., Yu, S., Interface Analysis Centre, University of Bristol, Bristol BS2 8BS, Department of Physics, University of Bristol, Bristol BS8 1TL, Department of Physics, University of Warwick, Coventry CV4 7AL, Innos Ltd., Southampton SO17 1BJ, and Department of Electrical and Electronic Engineering, University of Bristol, Bristol BS8 1UB. Fabrication and characterizations of proton-exchanged LiNbO{sub 3} waveguides fabricated by inductively coupled plasma technique. United States: N. p., 2006. Web. doi:10.1063/1.2191704.
Ren, Z., Heard, P.J., Hallam, K.R., Wotherspoon, Alex, Jiang, Q., Varrazza, R., Yu, S., Interface Analysis Centre, University of Bristol, Bristol BS2 8BS, Department of Physics, University of Bristol, Bristol BS8 1TL, Department of Physics, University of Warwick, Coventry CV4 7AL, Innos Ltd., Southampton SO17 1BJ, & Department of Electrical and Electronic Engineering, University of Bristol, Bristol BS8 1UB. Fabrication and characterizations of proton-exchanged LiNbO{sub 3} waveguides fabricated by inductively coupled plasma technique. United States. doi:10.1063/1.2191704.
Ren, Z., Heard, P.J., Hallam, K.R., Wotherspoon, Alex, Jiang, Q., Varrazza, R., Yu, S., Interface Analysis Centre, University of Bristol, Bristol BS2 8BS, Department of Physics, University of Bristol, Bristol BS8 1TL, Department of Physics, University of Warwick, Coventry CV4 7AL, Innos Ltd., Southampton SO17 1BJ, and Department of Electrical and Electronic Engineering, University of Bristol, Bristol BS8 1UB. Mon . "Fabrication and characterizations of proton-exchanged LiNbO{sub 3} waveguides fabricated by inductively coupled plasma technique". United States. doi:10.1063/1.2191704.
@article{osti_20779166,
title = {Fabrication and characterizations of proton-exchanged LiNbO{sub 3} waveguides fabricated by inductively coupled plasma technique},
author = {Ren, Z. and Heard, P.J. and Hallam, K.R. and Wotherspoon, Alex and Jiang, Q. and Varrazza, R. and Yu, S. and Interface Analysis Centre, University of Bristol, Bristol BS2 8BS and Department of Physics, University of Bristol, Bristol BS8 1TL and Department of Physics, University of Warwick, Coventry CV4 7AL and Innos Ltd., Southampton SO17 1BJ and Department of Electrical and Electronic Engineering, University of Bristol, Bristol BS8 1UB},
abstractNote = {This Letter reports the use of an inductively coupled plasma technique for fabrication of proton-exchanged (PE) LiNbO{sub 3} (LN) waveguides. Planar and stripe waveguides have been formed in Y-cut LN which are difficult to obtain with the conventional molten acid method due to the occurrence of surface damage. Secondary ion mass spectrometry, scanning electron microscopy, and infrared absorption spectrum characterization results revealed that a uniform vertical PE profile with a single low order crystal phase has been directly obtained as a result of this unique process. X-ray photoelectron spectroscopy characterization of the treated surface revealed the existence of NbO as the cause for a sometimes darkened surface and confirms the ability to completely restore the surface to LN by oxygen plasma treatment. Atomic force microscopy measurement confirms that good surface quality has been maintained after regeneration of the surface to LN.},
doi = {10.1063/1.2191704},
journal = {Applied Physics Letters},
number = 14,
volume = 88,
place = {United States},
year = {Mon Apr 03 00:00:00 EDT 2006},
month = {Mon Apr 03 00:00:00 EDT 2006}
}
  • The etching characteristics of congruent LiNbO{sub 3} single crystals including doped LiNbO{sub 3} and proton-changed LiNbO{sub 3} have been studied in reactive ion etching (RIE) and inductively coupled plasma (ICP) etching tools, using different recipes of gas mixtures. The effects of parameters including working pressure, RIE power, and ICP power are investigated and analyzed by measurement of etching depth, selectivity, uniformity, etched surface state, and sidewall profile by means of focused ion beam etching, energy-dispersive x-ray analysis, secondary ion mass spectroscopy, scanning electron microscopy, and surface profilometry. The effects of a sample carrier wafer coating have also been investigated. Optimizedmore » processes with high etching rates, good mask selectivity, and a near-vertical profile have been achieved. Ridge waveguides on proton-exchanged LiNbO{sub 3} have been fabricated and optically measured.« less
  • Inductively coupled plasma (ICP) etching is suitable for producing semiconductor structures with a high aspect ratio. While the morphology of the structures is very satisfactory, less is known about other aspects related to the process, but with potential influence in the optical performance of the devices. We present herein a study of the mechanical stresses produced by the ICP process in the fabrication of ridge waveguides in InP. Stresses purely induced by the process are revealed by the spectral analysis of the cathodoluminescence. A dependence of the stress distribution on the aspect ratio of the waveguides is demonstrated.
  • The planar and channel waveguides in z-cut LiNbO{sub 3} crystals have been fabricated by multienergy (2.2+1.8+1.6 MeV) oxygen ion implantation to a total dose of 6x10{sup 14} ions/cm{sup 2} at room temperature, followed by a thermal anneal at 260 deg. C for 30 min in dry oxygen atmosphere. The image and optical intensity distribution of the light in the waveguides were obtained by an end-fire coupling method. The guiding modes of the planar waveguides were measured by the prism-coupling method at 633 nm. The Rutherford backscattering/channeling technique was used to investigate the damage induced by oxygen ions after annealing treatment;more » the minimum yield of the spectra was 4.5%.« less
  • This paper reports that the nonlinear relationship between refractive index and hydrogen concentration has been experimentally determined for proton exchanged LiNbO{sub 3}, incorporating the effects of partial and full annealing. Complete annealing results in low-loss waveguides in the alpha phase with small surface index changes ({le}0.02). The anneal conditions needed to reach the alpha phase can be estimated using the measured temperature dependence of the anneal diffusion coefficient. A model is presented which attributes the index change in the alpha base to the addition of hydrogen and the loss of lithium, which is consistent with experimental results.
  • Infrared spectra of OH{sup −} groups in annealed proton-exchanged (APE) 5 mol. % MgO-doped LiNbO{sub 3} (MgO:LiNbO{sub 3}) crystals were studied using the Fourier transform infrared spectroscopy technique. Samples were prepared by benzoic acid proton-exchange followed with thermal annealing in oxygen. Evolutions of absorption peaks in APE MgO:LiNbO{sub 3} crystals were recorded and analyzed. Comparing with none-doped APE LiNbO{sub 3} crystals, a different phase transition behavior was found during thermal annealing. A periodically poled MgO:LiNbO{sub 3} slab waveguide was prepared using identical procedures, and the second harmonic generation (SHG) signals were measured. Comparing the obtained SHG results with the infrared spectra,more » relationships between the phase transitions and the recovery of second-order nonlinear coefficients during thermal annealing were investigated. Finally, a method for optimizing the performance of MgO:LiNbO{sub 3} waveguides was proposed.« less