Abstract
Spectroscopy in the mid-infrared region is an indispensable tool for
identifying molecular types in various fields, including physics,
chemistry, and medical sciences. However, conventional infrared light
sources, detectors, and noise from blackbody radiation have been the
obstacles to miniaturization and higher sensitivity of infrared
spectrometers. Quantum infrared spectroscopy, which uses visible and
infrared photon pairs in a quantum entangled state, has attracted
attention as a new sensing technology that enables infrared
spectroscopy with detectors in the visible range. However, the
bandwidth of conventional quantum entangled light sources is at most
1 µm or less, which hinders broadband measurements, which are
important in spectroscopic applications. Here we have realized an
ultra-broadband entangled state of visible–infrared photons with
wavelengths from 2 to 5 µm, harnessing a specially designed
nonlinear crystal with chirped poling structure inside. Furthermore,
we constructed a nonlinear quantum interferometer using the
ultra-broadband quantum entangled photons and realized broadband
infrared spectroscopy of inorganic and organic materials using a
visible detector made of silicon. Our results show that quantum
infrared spectroscopy can achieve ultra-broadband spectroscopic
measurements and pave the way for the highly sensitive, ultra-compact
infrared spectrometers using quantum entangled photons.
Funder
Ministry of Education, Culture, Sports,
Science and Technology
Core Research for Evolutional Science and
Technology
Cabinet Office, Government of Japan,
Public/Private RD Investment Strategic Expansion Program
Precursory Research for Embryonic Science
and Technology
Japan Society for the Promotion of
Science
Subject
Atomic and Molecular Physics, and Optics,Electronic, Optical and Magnetic Materials