Proposal for Being a KAGRA Member July 30, 2012 Kyuman Cho Department of Physics, Sogang Universit y

OVERVIEW I. Introduction −Sogang University −Photonics Lab II. Recent Researches on Interferometry III.Research Plan

I. Introduction

City Hall Sogang U. Seoul Han River

Yonsei Univ. Ewha Womans Univ. Sogang Univ. Hongik Univ. Shinchon ( 新村 ) Area

Overview History Established in 1960 by American Jesuits Faculty: 402 Full-time, tenure-track faculty members Students Undergraduate: 8,000 Graduate: 4,000 Over 1,000 international students Many courses taught in English Ranked #1 in National Customer Satisfaction Index survey in 1998, 1999, 2003, 2004, 2006 Ranked #1 in Korean Standards-Service Quality Index survey in 2007, 2009, 2010

Academic Program School of Humanities School of Social Sciences School of Natural Sciences Mathematics Physics Chemistry Life Science School of Engineering School of Economics School of Business Administration School of Communication

College of Natural Sciences

Department of Physics 17 Professors Particle Physics Condensed Matter Physics Optics BK21 Project World Class University Project Center for Quantum SpaceTime Center for Quantum Chaos Applications

Researches in Photonics Lab Modulation (Phase, Frequency Amplitude, Intensity) Demodulation (Phase, Frequency Amplitude, Intensity) Physical, Chemical, Biological Phenomena Linear and Non-Linear Optics Sensors Interferometry High-resolution scanning optical microscope High sensitivity readout sensors for biochips and micro-fluidic channels Measurement of magnetic birefringence in vacuum Precision sensor for measuring displacement, current, magnetic field, etc. BES for plasma diagnostics NSOM, etc FSO communications for subscriber service (fixed & moving) Visible light communications Data, Information Contents, etc. Data Recovery Optical Communications Measurements of Optical Parameters Transmission Line Fiber & FSO

Members and Collaborators Current Members Post Doctoral Fellow: Dr. Youngkyu Park Ph.D. Students: − Seung Hyun Yoon − Seang Hor Eang − Joonkyu Park Undergraduate Intern: Yongjae Kim International Collaborators Prof. Christopher C. Davis, University of Maryland, USA Prof. Anatoly Zayatts, Kings College, UK Dr. Igor Smolyaninov, BAE System, USA Domestic Collaborators from Universities: Korea Univ., Postech, Yonsei Univ., Ewha Univ., etc. Research Institutions: ETRI, KIST, KETI, etc. Industries: POSCO, GSI, NanoStorage, KAC, etc.

Recent Researches on Interferometry

Research Subjects One of the pioneers in the homodyne and heterodyne I/Q-interferometer: The 1 st version of the homodyne and heterodyne I/Q-interferometer was developed in 1994 and 1995, respectively. Have been designing and optimizing homodyne and heterodyne I/Q-interferometers for various applications: Scanning interferometer biosensors, vibrometer, and the other high sensitivity and wide dynamic range measurements in both academic and industrial applications Have been working on feasibility study for measuring magnetically induced birefringence in vacuum: A balanced homodyne scheme was proposed in Improved version of the MIBD was submitted to NSF and KRF in 2010 and 2012, respectively. Still looking for a proper funding.

Optical I/Q-Demodulator PBS1 PBS2 BS or PBS HWP QWP Can measure amplitude and phase change of the probe beam simultaneously No need for feedback control to maintain optimum sensitivity

Application Example Scanning Interferometer for complex surface diagnostics

RF I/Q-Demodulator

Application Example Scanning Interferometer for complex surface diagnostics

Application Example Phase and amplitude images of a patterned surface

Application Example Wide measurement range interferometer An astigmatic position sensing scheme is integrated to the heterodyne I/Q-interferometer. The interference signal is used for high resolution measurement while the astigmatic sensor is used for wide range measurement.

Application Example Scanning results (step height  3 μm)

Application Example New arrangement using double pass in AOM

 The equivalent minimum displacement ~ 5 x m Application Example Vibration Measurement

The topography (a), amplitude (b), and color-scaled amplitude (c) Application Example Scanning microscopy

In Out Application Example Readout sensor for a fluidic channel

Sample I Q Dual mode laser OL K. H. Kwon, B. S. Kim, and K. Cho, OPTICS EXPRESS, 16, (2008) Dual mode laser OL Constant-Phase Scanning Heterodyne Interferometer BS : Beam splitter PBS : Polarization Beam Splitter POL : Polarizer M : Mirror HWP : Half Wave Plate QWP : Quarter Wave Plate PD : Photo Diode PZT : Piezoelectric Transducer OI : Optical isolator OL : Objective Lense Application Example

The proposed microscope can measure both amplitude and phase simultaneously. The reflectivity image of the constant-phase scanning microscope is more clear than that of the HIQI. (a), (c) : constant-phase scheme, (b), (d): conventional scheme Application Example Scanning Results

Proposed Scheme for Measuring MILB Laser QWP PBS M1 M2 Magnet OIPol PD1 PD2 DA Two Faraday rotators are used to rotate the modulation principal axes. This scheme can provide the same modulation effects as rotating the magnet. The modulation frequency can go up to tens of Hz which is high enough to minimize 1/f-noise. No possible artifacts can be expected at the measurement frequency. Current Source CP FR(  F ) FR(-  F ) AA

Application Example Proposed scheme for measuring MIB

Research Plan

Advanced Lab for GWD Will do our best to get a proper research grant A big grant proposal has been submitted. Keep looking for grant opportunities if it is not awarded. Will concentrate on the researches on GWD. Perform extensive researches on GWD Create new ideas for improving the sensitivity of the GWD Establish a lab for building a prototype interferometer. Gaining experiences on the large scale interferometer. Testing new ideas for the GWD Establish active research network with KAGRA members Arrange regular meetings. (Ex: Prof. Shiniji Miyoki’s visit) Exchange knowledge, ideas, and members.

Suggested KAGRA Collaboration Members Prof. Christopher C. Davis, Dept. of ECE, Univ. of MD. Mentor of the Photonics Lab. Tens of years of experiences on interferometry, sensors, and optical communications Collaborator for designing interferometric measurement scheme for MIB. Dr. Youngkyu Park, Dept. of Phys., Sogang University Ph.D. Students in Dept. of Phys., Sogang Univ. Seung Hyun Yoon Seang Hor Eang Joonkyu Park