title: Investigation of second- and third-harmonic generation in few-layer gallium selenide by multiphoton microscopy.
abstract: Gallium selenide (GaSe) is a layered semiconductor and a well-known nonlinear optical crystal. The discovery of graphene has created a new vast research field focusing on two-dimensional materials. We report on the nonlinear optical properties of few-layer GaSe using multiphoton microscopy. Both second- and third-harmonic generation from few-layer GaSe flakes were observed. Unexpectedly, even the peak at the wavelength of 390 nm, corresponding to the fourth-harmonic generation or the sum frequency generation from third-harmonic generation and pump light, was detected during the spectral measurements in thin GaSe flakes.
authors.affiliation: Aalto University, Department of Micro and Nanosciences, Tietotie 3, FI-02150 Espoo, Finland.
authors.forename: Lasse
authors.initials: L
authors.lastname: Karvonen
authors.affiliation: Aalto University, Department of Micro and Nanosciences, Tietotie 3, FI-02150 Espoo, Finland.
authors.forename: Antti
authors.initials: A
authors.lastname: Säynätjoki
authors.affiliation: University of Arizona, College of Optical Sciences, 1630 E University Blvd, Tucson, AZ 85721, USA.
authors.forename: Soroush
authors.initials: S
authors.lastname: Mehravar
authors.affiliation: Technische Universität Chemnitz, Semiconductor Physics, Chemnitz 09107, Germany.
authors.forename: Raul D
authors.initials: RD
authors.lastname: Rodriguez
authors.affiliation: Technische Universität Chemnitz, Semiconductor Physics, Chemnitz 09107, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Hartmann
authors.affiliation: Technische Universität Chemnitz, Semiconductor Physics, Chemnitz 09107, Germany.
authors.forename: Dietrich R T
authors.initials: DR
authors.lastname: Zahn
authors.affiliation: University of Eastern Finland, Institute of Photonics, P.O. Box 111, FI-80101 Joensuu, Finland.
authors.forename: Seppo
authors.initials: S
authors.lastname: Honkanen
authors.affiliation: University of Arizona, College of Optical Sciences, 1630 E University Blvd, Tucson, AZ 85721, USA.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Norwood
authors.affiliation: 1] Aalto University, Department of Micro and Nanosciences, Tietotie 3, FI-02150 Espoo, Finland [2] University of Arizona, College of Optical Sciences, 1630 E University Blvd, Tucson, AZ 85721, USA [3] University of Eastern Finland, Institute of Photonics, P.O. Box 111, FI-80101 Joensuu, Finland.
authors.forename: N
authors.initials: N
authors.lastname: Peyghambarian
authors.affiliation: University of Arizona, College of Optical Sciences, 1630 E University Blvd, Tucson, AZ 85721, USA.
authors.forename: Khanh
authors.initials: K
authors.lastname: Kieu
authors.affiliation: Aalto University, Department of Micro and Nanosciences, Tietotie 3, FI-02150 Espoo, Finland.
authors.forename: Harri
authors.initials: H
authors.lastname: Lipsanen
authors.affiliation: Aalto University, Department of Micro and Nanosciences, Tietotie 3, FI-02150 Espoo, Finland.
authors.forename: Juha
authors.initials: J
authors.lastname: Riikonen