title: Mid-infrared transmitter and receiver modules for free-space optical communication.
abstract: We report on the experimental implementation of single-frequency fiber-laser pumped mid-infrared (mid-IR) transmitter and receiver modules for free-space communications. These modules enable frequency upconversion and downconversion between the 1550-nm telecom wavelength and the mid-IR, thus providing essential free-space transmission links with mid-IR single-frequency lasers in the 3.6 μm region. Specifically, based on difference frequency generation (DFG) in MgO-doped periodically poled LiNbO3(MgO:PPLN), the mid-IR transmitter produces 9.3-mW power at 3594 nm with 5-W pump power at 1083 nm (<10  kHz linewidth) and 3-W signal power at 1550 nm (<10  kHz linewidth), and the mid-IR receiver reproduces 12-μW power at 1550 nm with 4.7-W pump power at 1083 nm and 5-mW laser at 3594 nm. The whole modules are integrated into portable and compact devices by incorporating single-frequency fiber lasers, fiber amplifiers, DFG units, and related electronic circuits. In addition, the uses of all polarization-maintaining fiber configuration and well-controlled heat dissipation make the mid-IR transmitter and receiver exhibit a long-term stability.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Hao
authors.forename: Guoshen
authors.initials: G
authors.lastname: Zhu
authors.forename: Song
authors.initials: S
authors.lastname: Yang
authors.forename: Kangwen
authors.initials: K
authors.lastname: Yang
authors.forename: Tao
authors.initials: T
authors.lastname: Duan
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Xie
authors.forename: Kun
authors.initials: K
authors.lastname: Huang
authors.forename: Heping
authors.initials: H
authors.lastname: Zeng