Supplementary_Video.mp4

Simultaneous multiphoton imaging and writing is possible using the all-reflective microscope design. The video shows the third harmonic generated signal of a graphene layer on Silicon substrate imaged using 1540nm laser source. University of Arizona logo is printed on the sample using 1040nm laser and a separate set of scanners sharing the same optical path with the imaging laser source. Since the reflective design eliminates the chromatic aberration and dispersion issues, multiple sources can be deployed at the same time

Atomic Layer Engineering of Er-Ion Distribution in Highly Doped Er:Al₂O₃ for Photoluminescence Enhancement

For the past decade, erbium-doped integrated waveguide amplifiers and lasers have shown excellent potential for on-chip amplification and generation of light at the important telecommunication wavelength regime. However, Er-based integrated devices can only provide small gain per unit length due to the severe energy-transfer between the Er-ions at high concentration levels. Therefore, active ion concentrations have been limited to <1% levels in these devices for optimal performance. Here, we show an efficient and practical way of fabricating Er-doped Al₂O₃ with Er-concentration as high as ∼3.5% before concentration quenching starts to limit the C-band emission in our material. The Er-doped Al₂O₃ was fabricated by engineering the distribution of the Er-ions in Al₂O₃ with the atomic layer deposition (ALD) technique. By choosing a proper precursor for the fabrication of Er₂O₃, the steric hindrance effect was utilized to increase the distance between the Er-ions in the lateral direction. In the vertical direction, the distance was controlled by introducing subsequent Al₂O₃ layers between Er₂O₃ layers. This atomic scale control of the Er-ion distribution allows us to enhance the photoluminescence of our Er:Al₂O₃ material by up to 16 times stronger when compared to the case where the Er-concentration is ∼0.6%. In addition, long lifetime of approximately 5 ms is preserved in the Er-ions even at such high concentration levels. Thus, our optimized ALD process shows very promising potential for the deposition of optical gain media for integrated photonics structures

Rapid and Large-Area Characterization of Exfoliated Black Phosphorus Using Third-Harmonic Generation Microscopy

Black phosphorus (BP) is a layered semiconductor that recently has been the subject of intense research due to its novel electrical and optical properties, which compare favorably to those of graphene and the transition metal dichalcogenides. In particular, BP has a direct bandgap that is thickness-dependent and highly anisotropic, making BP an interesting material for nanoscale optical and optoelectronic applications. Here, we present a study of the anisotropic third-harmonic generation (THG) in exfoliated BP using a fast scanning multiphoton characterization method. We find that the anisotropic THG arises directly from the crystal structure of BP. We calculate the effective third-order susceptibility of BP to be ∼1.64 × 10^–19 m² V^–2. Further, we demonstrate that multiphoton microscopy can be used for rapid, large-area characterization indexing of the crystallographic orientations of many exfoliated BP flakes from one set of multiphoton images. This method is therefore beneficial for samples of areas ∼1 cm² in future investigations of the properties and growth of BP

Two-Photon Absorption in CdSe Colloidal Quantum Dots Compared to Organic Molecules

We discuss fundamental differences in electronic structure as reflected in one- and two-photon absorption spectra of semiconductor quantum dots and organic molecules by performing systematic experimental and theoretical studies of the size-dependent spectra of colloidal quantum dots. Quantum-chemical and effective-mass calculations are used to model the one- and two-photon absorption spectra and compare them with the experimental results. Currently, quantum-chemical calculations are limited to only small-sized quantum dots (nanoclusters) but allow one to study various environmental effects on the optical spectra such as solvation and various surface functionalizations. The effective-mass calculations, on the other hand, are applicable to the larger-sized quantum dots and can, in general, explain the observed trends but are insensitive to solvent and ligand effects. Careful comparison of the experimental and theoretical results allows for quantifying the range of applicability of theoretical methods used in this work. Our study shows that the small clusters can be in principle described in a manner similar to that used for organic molecules. In addition, there are several important factors (quality of passivation, nature of the ligands, and intraband/interband transitions) affecting optical properties of the nanoclusters. The larger-size quantum dots, on the other hand, behave similarly to bulk semiconductors, and can be well described in terms of the effective-mass models

Rapid and Large-Area Characterization of Exfoliated Black Phosphorus Using Third-Harmonic Generation Microscopy

Black phosphorus (BP) is a layered semiconductor that recently has been the subject of intense research due to its novel electrical and optical properties, which compare favorably to those of graphene and the transition metal dichalcogenides. In particular, BP has a direct bandgap that is thickness-dependent and highly anisotropic, making BP an interesting material for nanoscale optical and optoelectronic applications. Here, we present a study of the anisotropic third-harmonic generation (THG) in exfoliated BP using a fast scanning multiphoton characterization method. We find that the anisotropic THG arises directly from the crystal structure of BP. We calculate the effective third-order susceptibility of BP to be ∼1.64 × 10^–19 m² V^–2. Further, we demonstrate that multiphoton microscopy can be used for rapid, large-area characterization indexing of the crystallographic orientations of many exfoliated BP flakes from one set of multiphoton images. This method is therefore beneficial for samples of areas ∼1 cm² in future investigations of the properties and growth of BP