Mid-infrared photon counting and resolving
via efficient frequency upconversion
KUN HUANG,
1,
*YINQI WANG,
1
JIANAN FANG,
1
WEIYAN KANG,
2
YING SUN,
2
YAN LIANG,
2
QIANG HAO,
2
MING YAN,
1
AND HEPING ZENG
1,3,4,5,6
1
State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
2
School of Optical Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
3
Jinan Institute of Quantum Technology, Jinan 250101, China
4
CAS Center for Excellence in Ultra-intense Laser Science, Shanghai 201800, China
5
Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
6
e-mail: hpzeng@phy.ecnu.edu.cn
*Corresponding author: khuang@lps.ecnu.edu.cn
Received 18 September 2020; revised 23 December 2020; accepted 27 December 2020; posted 5 January 2021 (Doc. ID 410302);
published 1 February 2021
Optical detectors with single-photon sensitivity and large dynamic range would facilitate a variety of applications.
Specifically, the capability of extending operation wavelengths into the mid-infrared region is highly attractive.
Here we implement a mid-infrared frequency upconversion detector for counting and resolvi ng photons at 3 μm.
Thanks to the spectrotemporal engineering of the involved optical fields, the mid-infrared photons could be
spectrally translated into the visible band with a conversion efficiency of 80%. In combination with a silicon
avalanche photodiode, we obtained unprecedented performance with a high overall detection efficiency of
37% and a low noise equivalent power of 1.8 × 10
−17
W∕Hz
1∕2
. Furthermore, photon-number-resolving detec-
tion at mid-infrared wavelengths was demonstrated, for the first time to our knowledge, with a multipixel photon
counter. The implemented upconversion detector exhibited a maximal resolving photon number up to 9 with a
noise probability per pulse of 0.14% at the peak detection efficiency. The achieved photon counting and resolving
performance might open up new possibilities in trace molecule spectroscopy, sensitive biochemical sensing, and
free-space communications, among others.
© 2021 Chinese Laser Press
https://doi.org/10.1364/PRJ.410302
1. INTRODUCTION
The mid-infrared (MIR) wavelength region is of great interest
for a variety of applications as wide-ranging as environmental
monitoring, molecular spectroscopy, biomedical sensing, and
free-space communication [1,2]. In these envisioned scenarios,
sensitive MIR detection is highly demanded to access dramati-
cally improved performance in terms of detection sensitivity,
working distance, or imaging functionality [3]. So far, tremen-
dous progress has been witnessed in developing MIR detectors
based on either conventional semiconductors of indium anti-
monide (InSb) and mercury cadmium telluride (MCT), or
emerging materials of colloidal quantum dots [4], graphene
plasmons [5], and black phosphorus [6]. However, the noise-
equivalent power (NEP) is typically limited to about
pW∕Hz
1∕2
, far below the level of single-photon detection. The
attainable sensitivity could be improved with cryogenic oper-
ation for suppressing the intrinsic blackbody radiation and dark
current. Notably, MIR single-photon detection has been ac-
cessed by superconducting nanowire detectors [7], albeit with
additional complexity of a bulky cooling system. Very recently,
a broadband response window from 1.55 to 5.07 μm was
achieved with an optimized width of MoSi-based nanowire
[8]. Nowadays, continuous endeavors have still been dedicated
to approaching efficient direct detection for MIR photons,
especially at room temperature.
Indeed, the performance of currently existing MIR detectors
is in marked contrast to the visible and near-i nfrared regions, in
which highly efficient and low-noise photon counting is avail-
able by commercial avalanche photodiodes (APDs) [9].
Especially, photon-number-resolving (PNR) capability has also
been readily achieved using a silicon-based multipixel photon
counter (Si-MPPC). The resulting single-photon sensitivity
and large dynamic range could not only support accurate and
rapid characterization of nonrepetitive optical signal at low-
light levels, but also facilitate quantum-optics experiments to
investigate multiphoton quantum states [10,11], measure high-
order correlation functions [12], and characterize Wigner
functions [13]. Moreover, photon-number identification also
constitutes a key enabler in promising protocols in quantum
information science, such as thresholded laser ranging [14],
Research Article
Vol. 9, No. 2 / February 2021 / Photonics Research 259
2327-9125/21/020259-07 Journal © 2021 Chinese Laser Press