title: All-Optical Wavelength Conversion by Picosecond Burst Absorption in Colloidal PbS Quantum Dots.
abstract: All-optical approaches to change the wavelength of a data signal are considered more energy- and cost-effective than current wavelength conversion schemes that rely on back and forth switching between the electrical and optical domains. However, the lack of cost-effective materials with sufficiently adequate optoelectronic properties hampers the development of this so-called all-optical wavelength conversion. Here, we show that the interplay between intraband and band gap absorption in colloidal quantum dots leads to a very strong and ultrafast modulation of the light absorption after photoexcitation in which slow components linked to exciton recombination are eliminated. This approach enables all-optical wavelength conversion at rates matching state-of-the-art convertors in speed, yet with cost-effective solution-processable materials. Moreover, the stronger light-matter interaction allows for implementation in small-footprint devices with low switching energies. Being a generic property, the demonstrated effect opens a pathway toward low-power integrated photonics based on colloidal quantum dots as the enabling material.
authors.forename: Pieter
authors.initials: P
authors.lastname: Geiregat
authors.affiliation: Optoelectronic Materials Section, TU Delft , 2628 CD Delft, The Netherlands.
authors.forename: Arjan J
authors.initials: AJ
authors.lastname: Houtepen
authors.forename: Dries
authors.initials: D
authors.lastname: Van Thourhout
authors.forename: Zeger
authors.initials: Z
authors.lastname: Hens
keywords: all-optical signal processing; intraband absorption; nanocrystals; transient absorption