Recent Journal papers.

 

1. E.A.Vinogradov, C.C.Davis, A.L.Dobryakov, Yu.E.Lozovik, and I.I. Smolyaninov, Laser Physics, 10, 76-80 (2000), "Electron injection dynamics through the Schottky barrier".

 

Abstract

Ultrafast dynamics of semiconductor microcavity modes in ZnSe/Cr structures was studied by femtosecond pump-supercontinuum probe spectroscopy in wide spectral region 1.6-3.2 eV for different pumping photon energies hw1 = 2.34 eV,   hw2 = 2.75 eV and  hw3 = 5.5 eV. The ultrafast process ~ 40 fs connecting with the excitation of nonequilibrium electrons of metal (i.e. boundary of the microcavity), which penetrate through the Schottky electron barrier into the semiconductor, was observed. Possible applications of these microcavities as femtosecond broad-band optical switch and as device for effective up-conversing are discussed.

 

 

2. I.I. Smolyaninov, H.Y. Liang, C.H. Lee, C.C. Davis, L.D. Rotter, and D.L. Kaiser, Proc.MRS, vol.596, 333-338 (2000) "Near-field second harmonic microscopy of thin ferroelectric films".

 

Abstract

Near-field second harmonic microscopy is ideally suited for studies of local nonlinearity and poling of ferroelectric materials at the microscopic level. Its main advantages in comparison with other scanning probe techniques are the possibility of fast time-resolved measurements, and substantially smaller perturbation of the sample under investigation caused by the optical probe. We report second harmonic imaging of the surface of thin BaTiO3 films obtained in a near-field microscopy setup using a Ti:sapphire laser system consisting of an oscillator and a regenerative amplifier operating at 810 nm. Optical resolution on the order of 80 nm has been achieved.

 

 

3. I.I. Smolyaninov, H.Y. Liang, S. Aggarwal, R. Ramesh, C.H. Lee, and C.C. Davis, Optics Letters, 25, 835-837 (2000) "Near-field second harmonic microscopy of thin ferroelectric films"

 

Abstract

We present a near-field optical technique for second harmonic imaging using tapered optical fiber tips externally illuminated with femtosecond laser pulses. Enhancement of the electric field at the tip of the fiber results in enhanced second harmonic generation (SHG) from the sample region near the tip. This SH emission is collected by the same tapered fiber. The spatial distribution and polarization properties of second harmonic generation from thin ferroelectric films and poled single crystal of BaTiO3 has been studied. A spatial resolution on the order of 80 nm has been achieved. Symmetry properties of the near-field SH signal allow us to recover local poling direction of individual ferroelectric domains in the film.  Thus, the described technique provides a novel tool for nanometer scale crystal analysis of polycrystalline samples.

 

 

4. I.I. Smolyaninov, L. Wasiczko, K. Cho, and C.C. Davis, Proc. SPIE, vol.4489, ... (2001) "Long distance 1.2 Gb/s optical wireless communication link at 1550 nm"

 

Abstract

Free space optical wireless communication is an attractive way of connecting vast numbers of urban area customers to the fiber optic communication network. We have designed and tested a prototype 2 km long 1.2 Gb/s optical wireless link operating at 1550 nm. An EDFA amplified signal from a standard fiber optic transmitter unit was sent via a small telescope to a 5 inch corner cube mounted on the roof of a building located over 1 km from the transmitter. An estimated 10 mWatt incident on the corner cube was reflected back to the transmitter/receiver unit, where the signal was successfully recovered. Using this test range we have tested the two-fold time-delayed diversity scheme. To date we have used only audio frequency data. Diversity delays of 5ms, and 10ms show significant reductions in the probability of a joint fade at a particular level. Delays beyond about 10ms do not significantly improve link performance. The system we have developed allows straightforward DWDM and polarization diversity extensions that would multiply the data communication rate by the number of channels used in the link. Design issues for such optical wireless systems, measurements of bit error rate, aperture averaging, and the use of non-imaging light collection at the receiver will be discussed. We believe that such optical wireless transmitter/receiver units, which operate as an extension of the fiber network offer a reliable and inexpensive solution for the "last mile" problem in optical communications.  

 

 

5.  I.I. Smolyaninov, H.Y. Liang, C.H. Lee, and C.C. Davis, Journal of Appl.Phys. 89, 206-211 (2001) "Local crystal analysis using near-field second harmonic microscopy: Application to thin ferroelectric films"

 

Abstract

Application of near-field optical second harmonic microscopy to nanometer scale crystal and strain analysis of thin polycrystalline ferroelectric films is described. The near-field signal is shown to be sensitive to local crystal orientation by experimental and theoretical studies of the polarization properties of second harmonic generation from a poled single crystal of BaTiO3. Spatial resolution of the order of 80 nm has been demonstrated by recovery of the local poling direction of individual ferroelectric domains in polycrystalline thin Pb(ZrxTi1-x)O3 films. Near-field strain-induced second harmonic generation from thin BaxSr1-xTiO3 films has also been studied, and an agreement between theory and experiment has been established. Thus, the technique described provides a novel tool for nanometer scale crystal and strain analysis of polycrystalline samples.

 

 

6. H.Y. Liang, I.I. Smolyaninov, C.H. Lee, C.C. Davis, V. Nagarajan, and R. Ramesh, Proc.MRS, vol. 655, CC8.9.1-CC8.9.6 (2001) "Near-field optical second harmonic imaging of polydomain structure of epitaxial PbZrxTi1-xO3 thin films"

 

Abstract

Near field optical second harmonic microscopy has been applied to imaging of the c/a/c/a polydomain structure of epitaxial PbZrxTi1-xO3 thin films in the 0<x<0.4 range. An uncoated adiabatically tapered fiber tip was employed in our microscope which, according to our previous research  could yeild a resolution of up to 80 nm. Experimentally measured near-field second harmonic images have been compared with the results of theoretical calculations. Good agreement between theory and experiment has been demonstrated. Thus, novel optical technique for nanometer scale ferroelectric domain imaging has been developed.

 

 

7. I.I. Smolyaninov, H.Y. Liang, C.H. Lee, C.C. Davis, V. Nagarajan, and R. Ramesh, Journal of Microscopy, 202, 250-254 (2001) "Near-field second harmonic imaging of the c/a/c/a polydomain structure of epitaxial

PbZrxTi1-xO3 thin films"

 

Abstract

Near-field optical second harmonic microscopy has been applied to imaging of the c/a/c/a polydomain structure of epitaxial PbZrxTi1-xO3 thin films in the 0<x<0.4 range. Comparison of the near-field optical images and the results of AFM and x-ray diffraction studies show that the optical resolution of the order of 100 nm has been achieved. Symmetry properties of the near-field second harmonic signal allow us to obtain good optical contrast between the local second harmonic generation in c- and a-domains. Experimentally measured near-field second harmonic images have been compared with the results of theoretical calculations. Good agreement between theory and experiment has been demonstrated.

 

 

8. I.I. Smolyaninov and C.C. Davis, Optics Letters 26, 1495-1497 (2001) "Micromachining of diamond using near-field scanning optical microscope"

 

Abstract

Direct-write laser micromachining of diamond on a submicrometer scale using a near-field scanning optical microscope with an uncoated tapered fiber tip has been demonstrated. Micromachined structures may be imaged in situ immediately after the modification of the sample. An early stage of ablation process, which is believed to be diamond conversion into graphite has been visualized.

 

 

9. I.I. Smolyaninov, V.N. Smolyaninova, C.C. Davis, S-W. Cheong, and R.L. Greene, Phys.Rev.Letters 87, 127204 (2001) "High resolution study of permanent photoinduced reflectivity changes and charge order domain switching in Bi0.3Ca0.7MnO3"

 

Abstract

We report near-field and far-field optical microscopic studies of photoinduced effects in charge-ordered Bi0.3Ca0.7MnO3. Unlike previously reported transient photoinduced effects in manganites, we have observed permanent reflectivity changes following local sample illumination with 488 nm light. High-resolution images of exposed regions reveal optical contrast on a submicrometer scale. This observation indicates that photonic band-gap structures may be created using holographic recording in manganites. We also present images of photoinduced charge-order domain switching in Bi0.3Ca0.7MnO3.

 

 

10. I.I. Smolyaninov and C.C. Davis, Materials Letters, 52/6, 408-411 (2002) "Micromachining of diamond using near-field scanning optical microscope"

 

Abstract

Direct-write laser micromachining of diamond on a submicrometer scale using a near-field scanning optical microscope with an uncoated tapered fiber tip has been demonstrated. Micromachined structures may be imaged in situ immediately after the modification of the sample. An early stage of ablation process, which is believed to be diamond conversion into graphite has been visualized.

 

 

Conference papers.

 

1. I.I. Smolyaninov, H.Y. Liang, S. Aggarwal, R. Ramesh, C.H. Lee, and C.C. Davis, "Near-field second harmonic microscopy of thin ferroelectric films", in Quantum Electronics and Laser Science Conference'2000, OSA Technical Digest (OSA, Washington DC, 2000), p.63.

 

Abstract

We present a near-field optical technique for second harmonic imaging using tapered optical fiber tips externally illuminated with femtosecond laser pulses. Enhancement of the electric field at the tip of the fiber results in enhanced second harmonic generation (SHG) from the sample region near the tip. This SH emission is collected by the same tapered fiber. The spatial distribution and polarization properties of second harmonic generation from thin ferroelectric films and poled single crystal of BaTiO3 has been studied. A spatial resolution on the order of 80 nm has been achieved. Symmetry properties of the near-field SH signal allow us to recover local poling direction of individual ferroelectric domains in the film.  Thus, the described technique provides a novel tool for nanometer scale crystal analysis of polycrystalline samples.

 

2. I.I. Smolyaninov, C.H. Lee, and C.C. Davis, "Giant enhancement of surface second harmonic generation in BaTiO3 due to photorefractive surface wave excitation", in Quantum Electronics and Laser Science Conference'2000, OSA Technical Digest (OSA, Washington DC, 2000), p.186-187.

 

Abstract

We report observation of strongly enhanced surface SHG in BaTiO3 due to excitation of a photorefractive surface electromagnetic wave. Surface SH intensity may reach 10-2 of the incident fundamental light intensity. Angular, crystal orientation, and polarization dependencies of this SHG are presented. Possible applications of this effect in nonlinear surface spectroscopy are discussed.

 

3. I.I. Smolyaninov}, H.Y. Liang, S. Aggarwal, R. Ramesh, C.H. Lee, and C.C. Davis, "Near-field second harmonic microscopy of thin ferroelectric films", presented at the 6th International Conference on Near-Field Optics, Twente, The Netherlands, August 2000

 

Abstract

Near-field optical second harmonic microscopy has been applied to imaging of the c/a/c/a polydomain structure of epitaxial PbZrxTi1-xO3 thin films in the 0<x<0.4 range. Comparison of the near-field optical images and the results of AFM and x-ray diffraction studies show that the optical resolution of the order of 100 nm has been achieved. Symmetry properties of the near-field second harmonic signal allow us to obtain good optical contrast between the local second harmonic generation in c- and a-domains. Experimentally measured near-field second harmonic images have been compared with the results of theoretical calculations. Good agreement between theory and experiment has been demonstrated.

 

4. I.I. Smolyaninov, K. Cho, and C.C. Davis, "Near-field optical tip characterization using photoexpansion of As2S3 glass", presented at the 6th International Conference on Near-Field Optics, Twente, The Netherlands, August 2000

 

Abstract

We present a simple technique to characterize the quality of near-field optical tips by using a photo expansion effect (PEE) [1] in As2S3 chalcogenide glass. Commercially available polished As2S3 windows were mounted on the sample stage of a near-field optical microscope and briefly (for a few seconds or a few minutes, depending on the type of the tip and the tip aperture size) exposed to 488 nm light from the microscope tip. In a similar way to previous experiments with some photoresists [2,3], the surface of the As2S3 glass expanded substantially where illuminated. Shear-force topographical images of the glass surface taken after the exposure provide a qualitatively good picture of the optical field distribution from the tip. This was confirmed in other measurements of the tip field distribution involving scanning of one tip with respect to another.

 

 

5. I.I. Smolyaninov, H.Y. Liang, C.H. Lee, C.C. Davis, V. Nagarajan, C. Ganpule, R. Ramesh, and E. Williams, "Near-field optical second harmonic imaging of the polydomain structure of epitaxial PbZrxTi1-xO3  thin films", presented at the Fall 2000 Meeting of the Materials Research Society, November 2000

 

Abstract

Near-field optical second harmonic microscopy has been applied to imaging of the c/a/c/a polydomain structure of epitaxial PbZrxTi1-xO3 thin films in the 0<x<0.4 range. Comparison of the near-field optical images and the results of AFM and x-ray diffraction studies show that the optical resolution of the order of 100 nm has been achieved. Symmetry properties of the near-field second harmonic signal allow us to obtain good optical contrast between the local second harmonic generation in c- and a-domains. Experimentally measured near-field second harmonic images have been compared with the results of theoretical calculations. Good agreement between theory and experiment has been demonstrated.

 

 

6. I.I. Smolyaninov, H.Y. Liang, C.H. Lee, C.C. Davis, and R. Ramesh "Nanometer scale crystal and strain analysis using near-field second harmonic microscopy: application to thin ferroelectric films", Bulletin of the American Physical Society, Vol.46, p.938 (2001),

 

Abstract

Application of near-field optical second harmonic microscopy to nanometer scale crystal and strain analysis of thin polycrystalline ferroelectric films is described. The near-field signal is shown to be sensitive to local crystal orientation by experimental and theoretical studies of the polarization properties of second harmonic generation from a poled single crystal of BaTiO3. Spatial resolution of the order of 80 nm has been demonstrated by recovery of the local poling direction of individual ferroelectric domains in polycrystalline thin Pb(ZrxTi1-x)O3 films. Near-field strain-induced second harmonic generation from thin BaxSr1-xTiO3 films has also been studied, and an agreement between theory and experiment has been established. Thus, the technique described provides a novel tool for nanometer scale crystal and strain analysis of polycrystalline samples.

 

 

7. I.I. Smolyaninov and C.C. Davis, "Micromachining of diamond using near-field scanning optical microscope"  in Quantum Electronics and Laser Science Conference'2001, OSA Technical Digest (OSA, Washington DC, 2001), p.578-579.

 

Abstract

Direct-write laser micromachining of diamond on a submicrometer scale using a near-field scanning optical microscope with an uncoated tapered fiber tip has been demonstrated. Micromachined structures may be imaged in situ immediately after the modification of the sample. An early stage of ablation process, which is believed to be diamond conversion into graphite has been visualized.

 

 

8. I.I. Smolyaninov and C.C. Davis, "Near-field optical imaging of periodic plasmon sources", in Quantum Electronics and Laser Science Conference'2001, OSA Technical Digest (OSA, Washington DC, 2001), p.172-173.

 

Abstract

Periodic array of surface plasmon sources has been designed and imaged using near-field optical microscopy.  Such arrays constitute a novel example of two-dimensional photonic crystal structures. They may find application in multi-channel plasmon chemical and biosensors.

 

 

9. I.I. Smolyaninov, L. Wasiczko, K. Cho, and C.C. Davis, "Long  distance 1.2 Gb/s optical wireless communication link at 1550 nm", presented at the SPIE conference on Free-Space Laser Communication and Laser Imaging, July 2001, San Diego, Ca

 

Abstract

Free space optical wireless communication is an attractive way of connecting vast numbers of urban area customers to the fiber optic communication network. We have designed and tested a prototype 2 km long 1.2 Gb/s optical wireless link operating at 1550 nm. An EDFA amplified signal from a standard fiber optic transmitter unit was sent via a small telescope to a 5 inch corner cube mounted on the roof of a building located over 1 km from the transmitter. An estimated 10 mWatt incident on the corner cube was reflected back to the transmitter/receiver unit, where the signal was successfully recovered. Using this test range we have tested the two-fold time-delayed diversity scheme. To date we have used only audio frequency data. Diversity delays of 5ms, and 10ms show significant reductions in the probability of a joint fade at a particular level. Delays beyond about 10ms do not significantly improve link performance. The system we have developed allows straightforward DWDM and polarization diversity extensions that would multiply the data communication rate by the number of channels used in the link. Design issues for such optical wireless systems, measurements of bit error rate, aperture averaging, and the use of non-imaging light collection at the receiver will be discussed. We believe that such optical wireless transmitter/receiver units, which operate as an extension of the fiber network offer a reliable and inexpensive solution for the "last mile" problem in optical communications.  

 

 

10. I.I. Smolyaninov and C.C. Davis, "Effect of atmospheric turbulence on bit-error rate in an on-off keyed optical wireless system and its implications for link design", Invited talk presented at the SPIE conference on Free-Space Laser Communication and Laser Imaging, July 2001, San Diego, Ca

 

Abstract

 

Atmospheric turbulence produces scintillation at an optical receiver, which leads to fading of the received signal. This fading affects the bit-error-rate (BER) of a digital signal in a way that depends on the depth of the fade, the decision threshold at the receiver, and the average signal-to-noise ratio. The degree of fading can be dramatically reduced by the use of a time-delayed diversity technique, which involves retransmission of the data stream after a short delay, and resynchronization of the received data streams