Broadband Measurements of Ultrasonic Waves by Using Optical Beam Deflection

bae jong-rim,Han Jinwoo,Min Byeong June 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.4

The technique of optical beam deflection by ultrasonic waves was developed in order to measure ultrasonic velocity and absorption in liquids. A laser beam is deflected by ultrasonic waves under the condition that the sound wavelength is larger than the laser beam's waist. The deflection angle is detected with a high-speed photodiode, yielding the time derivative of the pressure amplitude of the ultrasonic waves. A broadband ultrasonic pulse excited with a 3-MHz quartz transducer was observed as a function of the propagation distance. The ultrasonic velocity of pure water was measured as a function of temperature at 3 MHz. The spectral analysis of the pulsed waveform enabled absorption measurements in the range of 9 -- 50 MHz in water, cyclohexane, carbon tetrachloride, benzene and methyl acetate. The technique of optical beam deflection by ultrasonic waves was developed in order to measure ultrasonic velocity and absorption in liquids. A laser beam is deflected by ultrasonic waves under the condition that the sound wavelength is larger than the laser beam's waist. The deflection angle is detected with a high-speed photodiode, yielding the time derivative of the pressure amplitude of the ultrasonic waves. A broadband ultrasonic pulse excited with a 3-MHz quartz transducer was observed as a function of the propagation distance. The ultrasonic velocity of pure water was measured as a function of temperature at 3 MHz. The spectral analysis of the pulsed waveform enabled absorption measurements in the range of 9 -- 50 MHz in water, cyclohexane, carbon tetrachloride, benzene and methyl acetate.

Weak Value Measurement of an Optical Beam Deflection in Image Rotating Sagnac Interferometer

박상준,김형주,노재우 한국광학회 2012 Current Optics and Photonics Vol.16 No.3

We measured small optical beam deflection in an image rotating Sagnac interferometer. We used a weak value measurement scheme that involves a pre-selection, weak perturbation, and a post-selection procedure to obtain the amplified value of beam deflection. The amplification factor of the measured beam deflection varied from 11 to 63 depending on the settings of the post-selection polarizer in front of the photodetector and the settings of polarization compensator in the interferometer.

Detection sensitivity of the optical beam deflection method characterized with the optical spot size on the detector

Lee, E.J.,Park, Y.,Kim, C.S.,Kouh, T. Elsevier 2010 Current Applied Physics Vol.10 No.3

Here we describe the effect of the incident optical spot size upon the quadrant photodetector on the displacement detection sensitivity of the optical beam deflection method. By varying the size of the beam spot reaching the photodetector and measuring the optical responsivity, we have determined the optical detection sensitivity as a function of the optical spot size on the photodetector. Also, we have calculated the numerical value of the detection sensitivity with the Gaussian optical spot profile and compared with the experimental data. Both experimental and analytic studies show that the optical displacement detection sensitivity increases with the decrease in the width of the Gaussian optical spot. The study presented here will be beneficial in developing the nanomechanical displacement detection techniques based on the beam deflection method with a position-sensitive detector.

Detection sensitivity of the optical beam deflection method characterized with the optical spot size on the detector

Eun Joong Lee,Youngok Park,고태준,김철성 한국물리학회 2010 Current Applied Physics Vol.10 No.3

Here we describe the effect of the incident optical spot size upon the quadrant photodetector on the displacement detection sensitivity of the optical beam deflection method. By varying the size of the beam spot reaching the photodetector and measuring the optical responsivity, we have determined the optical detection sensitivity as a function of the optical spot size on the photodetector. Also, we have calculated the numerical value of the detection sensitivity with the Gaussian optical spot profile and compared with the experimental data. Both experimental and analytic studies show that the optical displacement detection sensitivity increases with the decrease in the width of the Gaussian optical spot. The study presented here will be beneficial in developing the nanomechanical displacement detection techniques based on the beam deflection method with a position-sensitive detector.

4분할 광 검출기 상의 광점 크기가 변위 측정감도에 미치는 영향

이은중(Eun Joong Lee),이진우(Jin Woo Lee),고태준(Taejoon Kouh) 한국자기학회 2008 韓國磁氣學會誌 Vol.18 No.2

In this paper, we have measured the effect of the optical spot size, incident upon the quadrant photodetector, on the optical displacement sensitivity of the optical beam deflection technique. We have built an optical displacement detection system based on the optical beam deflection method using 3 ㎽ He-Ne laser and measured the displacement sensitivity with changing the optical spot size on the quadrant photodetector. We have also calculated the changes in the optical displacement sensitivity as a function of the incident laser spot size by modeling a circular optical spot with constant laser intensity. Our experimental and theoretical studies show that the optical displacement sensitivity increases with the decrease in the optical spot size. This suggests that in the design of the optical motion detection systems with sub-nanometer sensitivity, the displacement sensitivity can be optimized by reducing the size of the incident optical spot on the detector.

Developing a Cantilever-type Near-field Scanning Optical Microscope Using a Single Laser for Topography Detection and Sample Excitation

Douglas Kagoiya Ng’ang’a,Luqman Ali,이용중,변지수 한국광학회 2021 Current Optics and Photonics Vol.5 No.3

The capabilities of the near-field scanning optical microscope (NSOM) for obtaining high resolution lateral topographical images as well as for mapping the spectroscopic and optical properties of a sample below the diffraction limit of light have made it an attractive research field for most researchers dealing with optical characteristics of materials in nano scales. The apertured NSOM technique involves confining light into an aperture of sub-wavelength size and using it to illuminate a sample maintained at a distance equal to a fraction of the sub-wavelength aperture (near-field region). In this article, we present a setup for developing NSOM using a cantilever with a sub-wavelength aperture at the tip. A single laser is used for both cantilever deflection measurement and near-field sample excitation. The laser beam is focused at the apex of the cantilever where a portion of the beam is reflected and the other portion goes through the aperture and causes local near-field optical excitation of the sample, which is then raster scanned in the near-field region. The reflected beam is used for an optical beam deflection technique that yields topographical images by controlling the probe-sample in nano-distance. The fluorescence emissions signal is detected in far-field by the help of a silicon avalanche photodiode. The images obtained using this method show a good correlation between the topographical image and the mapping of the fluorescence emissions.

The plastic optical fiber cantilever beam as a force sensor

Kulkarni, Atul,Na, Jeonggil,Kim, Youngjin,Kim, Taesung Wiley Subscription Services, Inc., A Wiley Company 2009 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS Vol.51 No.4

<P>This study reports use of inexpensive intensity-based plastic optical fiber (POF) in the form of cantilever beam to monitor the force. The cantilever consists of POF surface bonded on the surface of metal beams viz. spring steel (SS) and mild steel (MS) and subjected to force. The performance of the force sensor is evaluated during macro-bending caused because of the deflection of the beam by applied force. Experimentally obtained detector output of POF, which could be measured with negligible hysteresis is compared with finite element analysis in the range between 0.0098 and 19.613 N. The reproducibility of the sensor is observed in the limit of ±1%. The proposed sensor can replace stain gauge load cell to certain extent in some applications. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1020–1023, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24217</P>