Recent advances in solid-state organic lasers

Organic solid-state lasers are reviewed, with a special emphasis on works published during the last decade. Referring originally to dyes in solid-state polymeric matrices, organic lasers also include the rich family of organic semiconductors, paced by the rapid development of organic light emitting diodes. Organic lasers are broadly tunable coherent sources are potentially compact, convenient and manufactured at low-costs. In this review, we describe the basic photophysics of the materials used as gain media in organic lasers with a specific look at the distinctive feature of dyes and semiconductors. We also outline the laser architectures used in state-of-the-art organic lasers and the performances of these devices with regard to output power, lifetime, and beam quality. A survey of the recent trends in the field is given, highlighting the latest developments in terms of wavelength coverage, wavelength agility, efficiency and compactness, or towards integrated low-cost sources, with a special focus on the great challenges remaining for achieving direct electrical pumping. Finally, we discuss the very recent demonstration of new kinds of organic lasers based on polaritons or surface plasmons, which open new and very promising routes in the field of organic nanophotonics

Growth and characterization of semiconductor nanoparticles in porous sol-gel films

Published versio

Polariton panorama

In this brief review, we summarize and elaborate on some of the nomenclature of polaritonic phenomena and systems as they appear in the literature on quantum materials and quantum optics. Our summary includes at least 70 different types of polaritonic light–matter dressing effects. This summary also unravels a broad panorama of the physics and applications of polaritons. A constantly updated version of this review is available at https://infrared.cni.columbia.edu

The physics and chemistry of semiconductor nanocrystals in sol-gel derived optical microcavities

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2006.Vita.Includes bibliographical references.The incorporation of semiconductor nanocrystals (NCs) into sol-gel derived matrices presents both novel applications as well as a robust platform in which to investigate the nonlinear optical properties of NCs. This thesis summarizes our present understanding of the chemistry of the incorporation process and the applications and underlying optical physics that was gleaned from studying these NC-doped sol-gel structures. Chapter 2 describes the synthesis of NC-doped core-shell silica microsphere composites of tunable size and emission wavelength, as well as their subsequent use for in-vivo imaging of blood vessels. This chapter illustrates how an appreciation of the kinetics of the Stober process allowed for the achievement of highly monodisperse microsphere composites with a uniform incorporation of NCs. Chapter 3 reviews the requirements for achieving stimulated emission in CdSe NCs and details the development of NC-based lasers through sol-gel derived microcavities, from distributed feedback (DFB) grating structures to spherical microresonators exhibiting whispering-gallery mode lasing. Chapter 4 compares and explicates the differences between silica and titania as host matrices for NCs in terms of their chemical stability in the presence of solvents.(cont.) This chapter explores the possibility of integrating NC-based microcavity lasers with microfluidic networks, thus providing the potential to dynamically tune the optical properties of the laser through interaction with different solvent environments on a miniaturized scale. Extension of the spectral window of NC-based gain media is discussed in Chapter 5, where extremely fast non-radiative Auger relaxation processes encountered in blue-emitting CdSe NCs may be circumvented by employing an alternative semiconductor NC, CdS/ZnS. Through judicious chemistry CdS/ZnS NCs may be uniformly incorporated into a sol-gel derived microcavity to provide room temperature lasing at blue wavelengths. Finally, our investigation into the optical physics of NCs in sol-gel derived microcavities is summarized in Chapter 6, which describes our observation of stimulated emission from multiexcitonic states in CdSe/ZnS NCs incorporated into a titania matrix. We employ transient photoluminescence to optically characterize the emission from these multiexcitonic states, which we attribute to 1P3/2-1Pc transitions. A DFB structure is introduced onto the CdSe/ZnS-titania composite to facilitate simultaneous lasing at two distinct wavelengths.by Yinthai Chan.Ph.D

Photoluminescent Properties of Vacuum Deposited Cadmium Sulfide Films

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryJoint Services Electronics Program / DAAB 07-67-C-0199Army DAAK 02-67-C-0546Ope

Novel Optical Applications Based on Photon-phonon Interactions

The phenomena of photon-phonon interactions can be found in all forms of matters including gases, plasma, liquids and solids. The applications based on such interactions, including Raman scattering, Bragg Scattering, polariton resonance, phonon-assisted Antistoke photoluminescence, etc. has been intensively investigated. In this dissertation, we present our study of three novel applications in the field of THz generation, hot phonons in transistors, and optical refrigeration. In Chapter 1, we studied the backward propagating Terahertz (THz) generation using optical rectification in periodically poled LiNbO3 and LiTaO3 samples with ultrafast laser pulse excitation. With the LiNbO3 sample, we have generated the highest frequency at 4.8 THz at the poling period of 7.1 µm, corresponding to an output wavelength of 62.5 µm. We have observed an enhancement factor as large as 61 in the output power comparing to that generated from bulk LiNbO3, which was attributed to the phonon polariton resonance-enhanced nonlinear optical coefficients. For the LiTaO3 samples, we have reached the highest output power of nearly 100 µW. Based on our study, the effective second-order nonlinear coefficient of LiTaO3 are enhance by factors of from 3.7 to 23, leading to the enhancement of THz output powers. The enhancement is rooted in a polariton resonance at the frequency of 127 cm-1, which can be induced by the nonlinear mixing of two transverse-optical phonons due to strong anharmonicity of LiTaO3. We also designed a second wafer with significantly shorter poling periods, and indeed we have observed the entire resonant peak. In Chapter 2, we studied the hot phonon behavior of GaN high electron mobility transistors (HEMT). We mainly investigated our effort on two methods utilizing Raman scattering to measure the phonon temperature, i.e. the hot phonon population of GaN HEMT device under operation. The ultimate goal was to employ these methods on the study of isotope disorder introduced GaN device and verify whether its phonon behavior is optimized than that in normal devices. The first method extracts phonon temperatures from the ratio of Antistokes and Stokes Raman signal intensities, which requires complex experimental procedures and tendency to wrong temperature deductions. The second method is based on the fitting of phonon temperature to the shift of Stokes Raman peak model, which leads to simple and fast measurement while sophisticated analysis with strong dependence to sample material properties. Comparing two methods, we believe the second one is advantageous due to our limited experimental condition, and it can be improved with proper calibration of the model. In Chapter 3, we studied the upconverstion of photoluminescence (PL) from both a free-standing bulk GaN sample and a GaN nanowire sample. When the excitation energy is in the tail of bandgap edge, the PL upconverstion can be attributed to phonon-assisted Antistokes photoluminescence (ASPL). We explored the potential of laser cooling based on such a phenomena with the analysis of PL intensity trending with pump power, excitation wavelength, and temperature. Such analysis proves the fact that the ASPL we measured is originated in single photon process assisted by phonons