Advances in Lock-in Photothermal Sensing

by

Dr. Khine Nyunt

Date  : 9 April, 2008, Wednesday

Time  : 12:00PM -1:00PM

Venue: Room 6-4-02, Building 6, Level 4, Room 02,

Monash University, Jalan Lagoon Selatan, Sunway

Abstract:

      For the detection of signals which are either DC or slowly varying in time, a substantial reduction in noise may be obtained by decreasing the bandwidth of the detection electronics with a simple low-pass filter. This method is effective only until the shot and Johnson noise (which are proportional to the square root of the frequency bandwidth) become less significant than the flicker noise, whose amplitude increases as 1/f and is non-negligible below about 100 Hz. 

      In practice, the technique of shifting the measurement frequency from DC to f is itself limited, unless the modulation frequency f and the detection electronics can be locked together to prevent f from drifting relative to the bandpass of the narrow-band filter. The lock-in correlation procedure overcomes the drift problem while taking advantage of the cross-correlation effect. A broader spectrum of electronic signals can be recovered from noisy background with the lock-in correlation technology. The advantage of lock-in photothermal sensing technology over conventional thermography is not only of significantly improved sensitivity owing to the AC averaging technique, but also an improvement in spatial resolution of the images. In particular, the sin/cos correlation which is sensitive only to basic signal-harmonics, seems to be optimum for the lock-in photothermal sensing. The technique allows both amplitude image (for a greater dynamic range and precision of measurements) and phase image (in nondestructive testing, where the influence of local emissivity of the materials is an issue). Owing to the limits  of detector-camera wavelength range, the lock-in photothermal sensing techniques are already established with a spatial resolution down to 5 μm ( with < 3μW localized, heat-source).

      The focus of the technical talk “Advances in Lock-in Photothermal Sensing” concentrates on the theory and practice of phase-sensitive, coherent- and synchronous-detection, pulsed and phased, on-line lock-in correlation, data analysis, dynamic range, detection limit and degradation of spatial resolution of the technology. 

Speaker’s Profile:

Khine Nyunt received his B.Sc. degree in physics from the University of Rangoon, Rangoon, Burma, Master of Engineering (Electronic Engineering) from the University of Electro-communications, Tokyo, Japan and Doctor of Engineering (Electronic Engineering) from the University of Tokyo, Tokyo, Japan, respectively. Currently, he is a Senior Lecturer in the Faculty of Engineering, Multimedia University (MMU), Selangor, Malaysia.

      He taught physics at Rangoon University, Rangoon, Burma from 1969 to 1989. He served the Faculty of Engineering, Assumption University, Bangkok, Thailand, as Associate Dean and as Chairperson of Electronics Engineering Department, before migrating to Singapore. He was employed in 1991 by Advanced Micro Devices (AMD) Singapore as device-analyst, before joining the Singapore statutory, National Science and Technology (NSTB) Board. He was a Member of Technical Staff at the Microsystems, Modules and Components Department, Failure Analysis and Reliability Group, Institute of Microelectronics (IME), National University of Singapore (NUS), from 1993 to 2003.

      Dr. Khine was a member of the local organizing committee for MMU International Symposium on Information and Communications Technologies (M2USIC) 2005 and 2006; Asia Pacific Wireless Broadband Forum (AP-WBF) 2005, NICT-MMU Joint Workshop on Wireless Access Technology (WWAT) 2005; a member of Photonics Interest Group (PinG) Malaysia, and was at a session chair on Laser Metrology and Laser Sensor, First National Photonics Colloquium (NPC’05) 2005, ESSET, Kajang, Malaysia. He was also a member of the local MRS organizing committee for International Conference on Materials for Advanced Technologies (ICMAT’01) 2001 held in Singapore and was at a session chair of the Symposium D on Crystallization and Interfacial Processes.

      Dr. Khine is a Senior Member of IEEE Electron Device Society and a Member of Electronic Device Failure Analysis Society (EDFAS) of the ASM International.

For details, please contact:

Melanie Ooi (Email: This email address is being protected from spam bots, you need Javascript enabled to view it ; Phone: 03-55146238)