title: All-optical modulation in Mid-Wavelength Infrared using porous Si membranes.
abstract: We demonstrate for the first time the possibility of all-optical modulation of self-standing porous Silicon (pSi) membrane in the Mid-Wavelength Infrared (MWIR) range using femtosecond pump-probe techniques. To study optical modulation, we used pulses of an 800 nm, 60 femtosecond for pump and a MWIR tunable probe in the spectral range between 3.5 and 4.4 μm. We show that pSi possesses a natural transparency window centred around 4 μm. Yet, about 55% of modulation contrast can be achieved by means of optical excitation at the pump power of 60 mW (4.8 mJ/cm(2)). Our analysis shows that the main mechanism of the modulation is interaction of the MWIR signal with the free charge carrier excited by the pump. The time-resolved measurements showed a sub-picosecond rise time and a recovery time of about 66 ps, which suggests a modulation speed performance of ~15 GHz. This optical modulation of pSi membrane in MWIR can be applied to a variety of applications such as thermal imaging and free space communications.
authors.affiliation: Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham, Edgbaston B15 2TT, United Kingdom.
authors.forename: Sung Jin
authors.initials: SJ
authors.lastname: Park
authors.affiliation: Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham, Edgbaston B15 2TT, United Kingdom.
authors.forename: Ammar
authors.initials: A
authors.lastname: Zakar
authors.affiliation: Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham, Edgbaston B15 2TT, United Kingdom.
authors.forename: Vera L
authors.initials: VL
authors.lastname: Zerova
authors.affiliation: Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham, Edgbaston B15 2TT, United Kingdom.
authors.forename: Dimitri
authors.initials: D
authors.lastname: Chekulaev
authors.affiliation: Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham, Edgbaston B15 2TT, United Kingdom.|pSiMedica Ltd. Malvern Hills Science Park, Geraldine Road, Malvern, WR14 3SZ, United Kingdom.
authors.forename: Leigh T
authors.initials: LT
authors.lastname: Canham
authors.affiliation: Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham, Edgbaston B15 2TT, United Kingdom.
authors.forename: Andre
authors.initials: A
authors.lastname: Kaplan