A mid-infrared spectral measurment with 30 μm light spot using a monochromator

What is it about?

The minimization of light spot in optical spectroscopies is an important issue in characterizations of micro- & nano- devices. However, the so-called microsized spectral measurements are only limited with their spectral detectbility in the visible and near infrared (IR) range, i.e. with the wavelength of light less than 2 μm. For longer wavelengh measurements, one generall accesses to Fourier transform technique (FTT). However, the FFT meets the challenge to minimize the light spot for measurements, with which a light spot is generally of milimeter dimension. The present work successes to circumvent the difficulty by using a monochromator and has realized the measurement upto 5 μm with the light spot minized to tens of micrometers.

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Why is it important?

Until now, no spectral measurement with a monochromator generally reaches beyond near IR spectral range. Our work demonstrates the feasibilty in the photoconductiviy experiment. Furthermore, the optical spectroscopies for longer wavelengh range than near IR have scarcely achieved spatial resolution of micrometers. The present work demonstrates the measurement with a light spot as small as 30 μm in the mid-IR range.