^{1}, Songky Moon

^{1}, Sang-Bum Lee

^{1}, Jai-Hyung Lee

^{1}, Kyungwon An

^{1,a)}, Jeong-Bo Shim

^{2}, Hai-Woong Lee

^{2}and Sang-Wook Kim

^{3}

### Abstract

We have developed a technique for realizing a two-dimensional quadrupolar microcavity with its deformation variable from 0% to 20% continuously. We employed a microjet ejected from a noncircular orifice in order to generate a stationary column with modulated quadrupolar deformation in its cross section. Wavelength redshifts of low-order cavity modes due to shape deformation were measured and were found to be in good agreement with the wave calculation for the same deformation, indicating that the observed deformation is quadrupolar in nature.

This work was supported by a National Research Laboratory grant and by Korea Research Foundation grants (Nos. KRF-2002-070-C00044 and KRF-2005-070-C00058). One of the authors (S.W.K.) was supported by a KOSEF grant (No. R01-2005-000-10678-0).

I. INTRODUCTION

II. METHOD TO OBTAIN DISCRETE DEGREE OF DEFORMATION

III. METHOD TO OBTAIN CONTINUOUSLY TUNED DEGREE OF DEFORMATION

IV. SHAPE CONFIRMATION BY SPECTRUM ANALYSIS

A. Method and principle

B. Experimental results

C. Small deformation case

### Key Topics

- Optical microcavities
- 22.0
- Red shift
- 13.0
- Quadrupoles
- 10.0
- Fluorescence spectra
- 6.0
- Chaotic dynamics
- 5.0

## Figures

(a) Model for the deformed microjet column. (b) Fabrication procedure of a noncircular orifice. The side view shows that the inner walls are inclined. The bottom view is a real image of a noncircular orifice.

(a) Model for the deformed microjet column. (b) Fabrication procedure of a noncircular orifice. The side view shows that the inner walls are inclined. The bottom view is a real image of a noncircular orifice.

Cross-sectional view of the deformation oscillation along the axis, given by Eq. (1) with . Initial deformation at is predetermined by the orifice. As the jet velocity is increased, the initial phase changes in such a way that is proportional to the velocity [see Eq. (7)]. Consequently, the deformations at antinodal planes, D1, D2, D3,… can be increased as the jet velocity. The parameter values used for these plots are , , , , and .

Cross-sectional view of the deformation oscillation along the axis, given by Eq. (1) with . Initial deformation at is predetermined by the orifice. As the jet velocity is increased, the initial phase changes in such a way that is proportional to the velocity [see Eq. (7)]. Consequently, the deformations at antinodal planes, D1, D2, D3,… can be increased as the jet velocity. The parameter values used for these plots are , , , , and .

(a) Variation of deformation parameter according to the ejection pressure of the jet at D2–D5 positions. (b) For deformation below 4%, the deformation is tunable by selecting different antinodal planes at a fixed jet pressure of .

(a) Variation of deformation parameter according to the ejection pressure of the jet at D2–D5 positions. (b) For deformation below 4%, the deformation is tunable by selecting different antinodal planes at a fixed jet pressure of .

(a) Cavity-modified fluorescence spectra observed at D3 as the jet pressure is varied. A particular mode of a good visibility marked by arrows is followed as the jet pressure is changed. (b) Observed wavelength shifts of the particular mode in (a), measured for the jet pressure varied at a small interval, are denoted by filled squares. Wavelength blueshifts due to the area contraction as the pressure is increased are represented by filled circles. The wavelength shifts due to the deformation only, denoted by crosses, are obtained by subtracting the latter from the former. Error bars are smaller than the symbol sizes.

(a) Cavity-modified fluorescence spectra observed at D3 as the jet pressure is varied. A particular mode of a good visibility marked by arrows is followed as the jet pressure is changed. (b) Observed wavelength shifts of the particular mode in (a), measured for the jet pressure varied at a small interval, are denoted by filled squares. Wavelength blueshifts due to the area contraction as the pressure is increased are represented by filled circles. The wavelength shifts due to the deformation only, denoted by crosses, are obtained by subtracting the latter from the former. Error bars are smaller than the symbol sizes.

(a) Wavelength shifts in the small deformation region. Oscillating pattern shows the deformation effect, and the underlying slope is due to the area expansion as the jet goes up. (b) Wavelength shifts due to the area expansion can be obtained by joining the local minima in (a), corresponding to no deformation. (c) Wavelength shifts due to deformation only is obtained by subtracting the shifts due to the area expansion in (b) from the total shifts in (a). Solid lines are the fits. The fitting parameters in (c) are , , , and for . Error bars are smaller than the point sizes.

(a) Wavelength shifts in the small deformation region. Oscillating pattern shows the deformation effect, and the underlying slope is due to the area expansion as the jet goes up. (b) Wavelength shifts due to the area expansion can be obtained by joining the local minima in (a), corresponding to no deformation. (c) Wavelength shifts due to deformation only is obtained by subtracting the shifts due to the area expansion in (b) from the total shifts in (a). Solid lines are the fits. The fitting parameters in (c) are , , , and for . Error bars are smaller than the point sizes.

Observed wavelength redshifts vs the degree of deformation measured by the diffraction technique. Solid line is the calculated redshift from the perimeter of a quadrupole, open triangles are the result of wave calculation for the same cavity, and filled squares are the experimental results. Vertical error bars are smaller than the point size.

Observed wavelength redshifts vs the degree of deformation measured by the diffraction technique. Solid line is the calculated redshift from the perimeter of a quadrupole, open triangles are the result of wave calculation for the same cavity, and filled squares are the experimental results. Vertical error bars are smaller than the point size.

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