22-10-2016, 02:56 PM
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Photonics uses photons to probe and manipulate matter. Since the invention of
lasers in the 1960s, which provide an intense source of coherent radiation, photonics
techniques have revolutionized several areas such as high-bandwidth communication
channels. The development of ultrafast lasers, which are capable of producing laser
pulses with pulse widths as low as a few femto-seconds (fs, 1x10-15 s), enabled the use of
non-linear optical processes for high-resolution imaging, providing novel information
about biological systems. The high instantaneous power delivered by such ultrafast
lasers while keeping very low radiation energy levels, enables the use of such lasers for
micro-surgery or even laser-ablation of tissues. With the development of
nanotechnology and plasmonics, we today have optically responsive nanoparticles that
can used as novel image contrast agents or selective removal of cancer tissues by the
heat generated due to photoabsorption of the nanoparticles, which are selectively taken
up by the tumor cells.
Biophotonics refers to the topics that lie at the intersection of Biology and
Photonics. In recent times there has been significant development in the use of optical
techniques to probe and manipulate biological systems. Optical microscopy using
fluorescence emission has reached a point where structures even as small as 50 nm can
be imaged using super resolution imaging techniques, breaking the diffraction barrier
of optical resolution. Similarly, techniques such as optical tweezers, highly sensitive
molecular sensors and so on allow one to probe bio-physical phenomena at the single
molecular level. Biophotonics is a rapidly growing field with immense opportunities to
researchers with pretty much any educational background. Biologists and Chemists can
contribute in the development of molecules with engineered optical response for
various applications such as image contrast agents, photosensitizers for photodynamic
therapy and so on. Physicists can contribute in the development of novel imaging and
sensing modalities that push the capabilities of tools to probe complex biological
systems. Engineers can contribute in areas such as the fabrication and miniaturization
of devices with automated process flow for high throughput bio-analytical studies.
There is also requirement for applied mathematicians, computer scientists and
statisticians for developing computationally efficient techniques for analyzing massive
volumes of data that modern bio-analytical and imaging systems produce.
This course is intended to provide a basic introduction to the field of
Biophotonics to students from a wide range of academic background from pure science
to Engineering. The attempt has been to communicate the essential ideas behind some
of the current techniques being used in the field with appropriate background materials
while avoiding most of the mathematical details for the sake of simplicity. The material
presented here has been divided into 4 modules. The first module introduces basic
notions in geometric, wave and electromagnetic description of light. The second module
introduces the quantum picture of matter and the photon. The third module describes
microscopy techniques and optical manipulation and the last module describes some
optical biosensing techniques. The hope is that this material will provide a starting
point for students desirous of advanced study in this field. A list of textbooks and
online material suitable for advanced study is listed at the end of the last module.
I would like to thank Wikipedia Commons and several open access research
journals for some of the images that have been used in the preparation of this material.