Damien Teyssieux

Near-infrared thermography using a charge-coupled device camera: Application to microsystems

Using near-infrared thermography microscopy and a low-cost charge-coupled device (CCD) camera, we have designed a system which is able to deliver quantitative submicronic thermal images. Using a theoretical model based on Plancks law and CCD sensor properties allowed us to determine a minimal theoretical detection temperature and an optimal temperature sensitivity of our system. In order to validate this method, we show a good relationship between a theoretical study and a thermal measurement of a microsample.

Quantitative thermal microscopy using thermoelectric probe in passive mode

A scanning thermal microscope working in passive mode using a micronic thermocouple probe is presented as a quantitative technique. We show that actual surface temperature distributions of microsystems are measurable under conditions for which most of usual techniques cannot operate. The quantitative aspect relies on the necessity of an appropriate calibration procedure which takes into account of the probe-to-sample thermal interaction prior to any measurement. Besides this consideration that should be treated for any thermal contact probing system, the main advantages of our thermal microscope deal with the temperature available range, the insensitivity to the surface optical parameters, the possibility to image DC, and AC temperature components up to 1 kHz typically and a resolution limit related to near-field behavior.

Scanning thermal microscopy based on a quartz tuning fork and a micro-thermocouple in active mode (2ω method)

A novel probe for scanning thermal microscope using a micro-thermocouple probe placed on a Quartz Tuning Fork (QTF) is presented. Instead of using an external deflection with a cantilever beam for contact detection, an original combination of piezoelectric resonator and thermal probe is employed. Due to a non-contact photothermal excitation principle, the high quality factor of the QTF allows the probe-to-surface contact detection. Topographic and thermal scanning images obtained on a specific sample points out the interest of our system as an alternative to cantilevered resistive probe systems which are the most spread.

Photo-thermal quartz tuning fork excitation for dynamic mode atomic force microscope

A photo-thermal excitation of a Quartz Tuning Fork (QTF) for topographic studies is introduced. The non-invasive photo-thermal excitation presents practical advantages compared to QTF mechanical and electrical excitations, including the absence of the anti-resonance and its associated phase rotation. Comparison between our theoretical model and experiments validate that the optical transduction mechanism is a photo-thermal rather than photo-thermoacoustic phenomenon. Topographic maps in the context of near-field microscopy distance control have been achieved to demonstrate the performance of the system.

Absolute phase and amplitude mapping of Surface Acoustic Wave fields

This paper describes the development of a scanning heterodyne interferometer for acoustic wave energy mapping. A robust optical double pass interferometer setup is presented, allowing absolute phase and absolute magnitude measurements of the out-of-plane vibration component witin a 5 to 1200 MHz frequency range, only limited by the photodetector bandwidth. By using a dedicated high frequency demodulator, the system is insensitive to the low-frequency mechanical vibration. The system is here used on single-port Surface Acoustic Wave, allowing for the identification of energy distribution as a function of operating frequency and the acoustic velocity over the Bragg mirrors surrounding the resonator. We envision such an instrument as a tool for assessing acoustic energy confinement allowing for optimizing resonator quality factors aimed at providing improved frequency source stability.

Thermal detectivity enhancement of visible and near infrared thermography by using super-resolution algorithm: Possibility to generalize the method to other domains

This paper reports on a method which allows a decrease in the minimal detectable temperature in visible and near infrared thermography. This original method permits an increase in the thermal sensitivity without loss of good spatial resolution. It is based on a binning operation and a super-resolution algorithm. The radiometric model and super-resolution method are presented. Measurements on two different samples show the enhancement of the thermal sensitivity and the capability of the method. Finally, the authors propose different ways in which the method can be applied.

Observation of band gaps in chirped interdigital transducers

A grating structure serves as the most fundamental element of inter-digital transducers (IDTs). IDTs are used for excitation and detection of surface acoustic waves (SAW) in Ultra wide band (UWB) SAW devices. Reflections on the metal fingers greatly affect the functionality of IDTs, and thus that of the SAW devices they are used in. Hence, this effect has been studied extensively and several models and theories have been proposed for this purpose. The signal properties of IDT devices can be controlled by varying several parameters like the number of fingers (electrodes) of the IDT or the spatial distribution of the pitch of the array of fingers. Here, we wish to study the generation and propagation of SAW inside a chirped IDT.

A differential optical interferometer for measuring short pulses of surface acoustic waves

HIGHLIGHTSTime‐delay interferometry suitable for measuring short SAW pulses is demonstrated.The working principle of the differential interferometer is described.A mathematical analysis of the interferometric measurement is presented.Interferometric, electrical, and theoretical measurements are compared and are found to be in good agreement.The effects of varying the path difference of the interferometer is studied. ABSTRACT The measurement of the displacements caused by the propagation of a short pulse of surface acoustic waves on a solid substrate is investigated. A stabilized time‐domain differential interferometer is proposed, with the surface acoustic wave (SAW) sample placed outside the interferometer. Experiments are conducted with surface acoustic waves excited by a chirped interdigital transducer on a piezoelectric lithium niobate substrate having an operational bandwidth covering the 200–400 MHz frequency range and producing 10‐ns pulses with 36 nm maximum out‐of‐plane displacement. The interferometric response is compared with a direct electrical measurement obtained with a receiving wide bandwidth interdigital transducer and good correspondence is observed. The effects of varying the path difference of the interferometer and the measurement position on the surface are discussed. Pulse compression along the chirped interdigital transducer is observed experimentally.

Development and characterization of a differential interferometer setup using ultra-wideband SAW devices

We consider the problem of measuring short surface acoustic wave pulses directly in the time domain. The time-shearing differential optical interferometer setup described in this work is extremely sensitive and requires noise calibration. In order to test the accuracy of the response of the interferometer, different parameters of the experimental setup are varied. An input chirp is used to excite surface acoustic waves (SAW) in the device within a frequency range of 200 MHz - 400 MHz. The responses measured at the output IDT, directly and by using the interferometer setup, are compared and the change in amplitude for the two measurements are studied.

Femtosecond heterodyne pump probe platform

We present a femtosecond heterodyne pump probe platform with electronically synchronized Ytterbium laser. The main goal of this platform is to provide thermal characterization at short space and time scales. Picosecond acoustic phenomena can also be observed and used to extract information such as acoustic wave velocities. Thermal conductivities and thermal interface resistances can be extracted for the different layers in the studied sample by fitting thermal models with experimental data. To characterize laterally structured samples, solid immersion lenses have been fabricated and used to increase the spatial resolution.