MRI: Development of Integrated Tunable Picosecond Optical Microscopy System with Multichannel Heterodyning Detector Array

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0216155SchmidtContinuous progress in microscopy and ultrafast optics has allowed researchers to investigatephenomena on ever smaller length and shorter time scales, leading to a multitude of novel applications. Here, the PIs propose to build a measurement system that combines both ultrahigh spatial and temporal resolution. This system will enable access to a whole new class of experiments for which both characteristics are required and will significantly enhance the research facilities at UC Santa Cruz. They propose to develop a system that integrates the temporal resolution of a tunable ultrafast Ti:Sapphire laser with the spatial resolution of an atomic force microscope with NSOM capabilities and a high-resolution photodetector array. The ultrashort optical pulses emanating from the Ti:Sapphire laser are fed into the fiber of the near-field microscope or focused directly on a sample using far-field optics. A subwavelength aperture at the output of the NSOM is used to emit or collect the light pulses, and creates a unique optical probe for investigating a wide variety of samples and substrates. The tunability of the Ti:Sapphire allows for a large accessible spectrum in the near-infrared while leaving options for future upgrades. The complete system will simultaneously have a time resolution of about 200fs and a spatial resolution of 100 nm.If funded, research projects and student training in nanoscale electronics will be carried out: One example for the ensuing research activities is the study of the dynamics of magnetization switching in single-domain metallic nanomagnets for high-density magnetic storage. Only the combination of both high spatial and temporal resolution will allow studying the dynamics of individual magnets. Knowledge of the magnetization reversal time is critical for assessing the intrinsic limitations for write-operations using such nanomagnets. Magneto-optic Kerr spectroscopy is capable of capturing reversal dynamics, but so far not with the required capabilities for single-domain magnets. The second project is spatially resolvedpicosecond ultrasonics. Here, the goal is to analyze interfaces below a metal-covered semiconductor surface, a situation typical for integrated circuits. By heating the metal with a short optical pulse, an acoustic wave is created that propagates inside the semiconductor and is partially reflected at interfaces. The depth of the interface can be determined from the return time of the reflection signal. In combination with the high spatial resolution of a near-field scanning microscope and a unique multichannel heterodyning detection method using a photodetector array, non-destructive high-resolution imaging of the wafer can be obtained.These examples clearly demonstrate the wide range of experiments that will become accessible. The main components (Ti-sapphire laser, AFM/NSOM) are each widely used state-of-the-art instruments and their combination which require significant development for pulse broadening compensation, polarization control and also multi-channel detector array will create unique capability for many more fields in nanotechnology, such as time-resolved spectroscopy of semiconductor quantum dots. Exciting collaborations across campus departments and with other universities are anticipated. The system will have broad impact on research and education in nanoscience. It will provide excellent training for students in several key areas of current interest such as nanoscopy, laser optics, and time-resolved spectroscopy. In addition, it will be integrated in a laboratory experiment for a nano-optics class that the P.I. is developing at UCSC as part of an NSF CAREER program.