Methods and Systems for On-Chip Spectrometry

Technology #18021

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Professor Juejun Hu
Department of Material Science and Engineering, MIT
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Professor Tian Gu
Department of Material Science and Engineering, MIT
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Derek Kita
Department of Material Science and Engineering, MIT
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Hongtao Lin
Department of Material Science and Engineering, MIT
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Jim Freedman
MIT Technology Licensing Officer - Chemicals, Instruments, Consumer Products
Patent Protection

Apparatus, Systems , and Methods for On-Chip Spectroscopy using Optical Switches

US Patent Pending

Methods And Systems For On-Chip Spectrometry

PCT Patent Application Filed
Miniature Spectrometer and Beam Splitter for an Optical Coherence Tomography on a Silicon Chip
Optical Express, 21 (14): 16648-56, Jul. 15, 2013
Integrated Photonic Crystal Spectrometers for Sensing Applications
Optics Communications, 282 (15): 3168-71, Aug. 1, 2009


  • Biological and chemical sensing
  • Portable sensing and lab-on-a-chip functionality

Problem Addressed

Advances in on-chip spectroscopy are resulting in improved chemical and biological sensing applications. Fourier Transform Infrared (FTIR) technology, a leading spectroscopy system, exhibits an enhanced signal-to-noise ratio over other spectroscopy designs by utilizing Fellgett’s advantage. To achieve this, FTIR spectrometers have a variable arm path length and use modulation of the index of refraction to enable spectral decomposition of light from the interferogram. However, this approach often requires discrete optical elements resulting in a costly and bulky design. In addition, it results in increased system complexity from mechanical moving parts and reduced system robustness. Many on-chip spectrometers use spectrum splitting, a much less effective spectrometry system, due to size and power constraints. These designs have a reduced signal-to-noise ratio because they lack the Fellgett advantage present in FTIR spectrometers.


The invention is a FTIR interferometer that extracts spectral density information through direct modification of the waveguide path. This results in an inexpensive and robust design that is compatible with on-chip integration. Direct modulation has also proved to be a far more effective method for spectral decomposition than modulating the index of refraction. Using direct modulation eliminates reliability problems, as there are not mechanical moving parts, and also features reduced complexity and increased system robustness. The invention is both highly tolerant of fabrication errors and extremely generic. It can be constructed on a wide variety of waveguiding platforms including silicon-on insulator, III-V semiconductors and polymers.


  • Superior spectral resolution compared to prior on-chip FTIR devices
  • Compatible with compact on-chip integration
  • Highly tolerant of fabrication errors
  • Inexpensive and simple FTIR sensor design without bulkiness
  • Generic design excellent on a wide array of on-chip waveguiding platforms