Mid-infrared electro-optic modulation in few-layer black phosphorus (Conference Presentation)

Abstract

Black phosphorus stands out from the family of two-dimensional materials as a semiconductor with a direct, layer-dependent bandgap in energy corresponding to the spectral range from the visible to the mid-infrared (mid-IR), as well as many other attractive optoelectronic attributes. It is, therefore, a very promising material for various optoelectronic applications, particularly in the important mid-IR range. While mid-IR technology has been advancing rapidly, both photodetection and electro-optic modulation in the mid-IR rely on narrow-band compound semiconductors, which are difficult and expensive to integrate with the ubiquitous silicon photonics. For mid-IR photodetection, black phosphorus has been proven to be a viable alternative. Here, we demonstrate electrooptic modulation of mid-IR absorption in few-layer black phosphorus under field applied by an electrostatic gate. Our experimental and theoretical results find that, within the doping range obtainable in our samples, the quantum confined Franz-Keldysh effect is the dominant mechanism of electro-optic modulation. Spectroscopic study on samples with varying thickness reveals strong layer-dependence in the inter-band transition between different subbands. Our results show black phosphorus is a very promising material to realizing efficient mid-IR modulators.Recently, two-dimensional (2D) materials, including graphene, various transition metal dichalcogenides, hexagonal boron nitride and black phosphorus (BP), have shown great potential

Widely tunable black phosphorus mid-infrared photodetector

“…The ability to tune the photoresponse of BP in a wide mid-IR spectral range implies that BP could be an alternative material for mid-IR photonics. The demonstration of tuning here is also distinctively different from previously results on BP optical property tuning with a single gate, in which both the Franz–Keldysh and Pauli-blocked Burstein–Moss effects 43 – 45 play a role. The Burstein–Moss effect 43 , 44 in highly doped BP leads to a blueshift of optical absorptions at high charge carrier densities due to blockings of low-energy optical transitions by band filling.…”

“…The Burstein–Moss effect 43 , 44 in highly doped BP leads to a blueshift of optical absorptions at high charge carrier densities due to blockings of low-energy optical transitions by band filling. The Franz–Keldysh effect 43 – 45 redshifts the BP absorption edge when the doping of BP is below ~3 × 10 12 cm −2 , while the Burstein–Moss dominates and blueshift of the absorption is expected at higher doping concentrations 43 , 44 . Here the dual-gate configuration provides an additional gate variable and allows us to reach the charge-neutrality position of BP at different biasing field, leading to significant redshift of the light absorption edge, highly desirable for mid-IR applications.…”