Search

The principle of detailed balance states that objects efficiently emitting radiation at a specific wavelength also efficiently absorb radiation at the same wavelength. This principle presents challenges for the design and performance of photonic devices, including solar cells, nanoantennas, and lasers. A design that successfully integrates the properties of an efficient emitter in one state and invisibility in another state is essential for various applications. In this work, we propose a novel nanolaser design based on a semiconductor nanoparticle with gain enveloped by a phase transition material that enables switching between lasing and cloaking (nonscattering) states at the same operating frequency without modifying the pumping conditions. We thoroughly investigate the operational characteristics of the nanolaser to ensure optimal performance. Our nanolaser design can function with both optical and electric pumping and exhibits the features of a thresholdless laser due to its high beta-factor and strong Purcell enhancement in the tightly confined Mie resonance mode. Additionally, we develop a reconfigurable metasurface comprising lasing-cloaking metaatoms capable of transitioning from lasing to a nonscattering state in a fully reversible manner.

Light sources with ultra-low energy consumption and high performance are required to realize optical interconnects for on-chip communication. Photonic crystal (PhC) nanocavity lasers are one of the most promising candidates for this role. In this work, a continuous-wave PhC nanolaser with an ultra-low threshold current of 10.2 µA emitting at 1540 nm and operated at room temperature is demonstrated. The lasers are InP-based bonded on silicon (Si), and comprise a buried heterostructure active region and lateral p–i–n junction, feature CMOS-compatible drive voltage, and exhibit low self-heating. Carrier leakage is a fundamental limitation of the lateral pumping scheme that is identified as unwanted spontaneous emission from the InP p–i interface, limiting the injection efficiency to 3% which further decreases at higher current. The effect of fabrication disorder and p-doping absorption on the Q-factor is studied experimentally showing that p-doping limits the Q-factor to 8000, with a p-doping absorption coefficient of 120 cm−1.

The emergence of nanolasers over the past two decades has helped enable a plethora ofnovel applications such as optical communications, on-chip interconnects, sensing and superresolution imaging. Particularly for the field of computing/communication, nanolasers have become an intriguing area of research as photonic integrated circuits (PICs) of the future would require nanoscale light sources. To that end, nanolasers based on a variety of architectures and underlying physics have been demonstrated in the literature. Metallo-dielectric nanolasers (MDNLs) are particularly attractive since they combine the advantages of ultrasmall footprints and low thresholds offered by other nanolaser types while still offering electromagnetic isolation, telecom-band operation and current injection. In this dissertation, we mainly focus on exploring additional attributes of MDNLs that further lend credence to their suitability for dense integration on-chip. One of these desirable traits we study includes reversible wavelength tuning (upto 8.35 nm) and intensity modulation of an MDNL based on an external electric field (Chapter 2). More importantly, we report that this electric-field based intensity modulation can be performed at high-speeds of upto 400 MHz (limited only by the detector bandwidth). A second characteristic appropriate for dense integration involves investigating the presence of coupling when two MDNLs are designed in proximity on-chip (Chapter 3). Our results indicate that not only does coupling occur, but it can also be inhibited if independent operation of the emitters is required. We further explore the concept of coupling but with regards to phase-locking two high-b, laterally coupled lasers (Chapter 4). We found that high b values, that are usually only exhibited in nanolasers such as MDNLs, help significantly increase the stable phase-locking regions for two coupled lasers. Additionally, high b can also lead to a wider range of phase differences attainable for a

Micro- and nanolasers are emerging optoelectronic components with many properties still to be explored and understood. On the one hand, they make it possible to address fundamental physical questions in the border area between classical physics and quantum physics, on the other hand, they open up new application perspectives in many areas of photonics. This progress report provides an overview of the exciting developments from conventional semiconductor lasers toward nanoscale lasers, whose function relies on increased light–matter interaction in low-mode-volume resonators and unconventional gain concepts. The latest advances in the physical understanding of light emission from high-β lasers, in which a large part of the spontaneous emission is coupled into the laser mode, are highlighted. In the limit of β = 1, this leads to thresholdless lasing and it is shown that quantum optical characterization is required to fully explore the underlying emission processes. In addition, emerging nanolaser concepts based on Fano resonators, topological photonics, and 2D materials are presented. Open questions, future prospects, and application scenarios of high-β lasers in integrated photonics, quantum nanophotonics, and neuromorphic computing are discussed.

The emergence of nanolasers over the past two decades has helped enable a plethora ofnovel applications such as optical communications, on-chip interconnects, sensing and superresolution imaging. Particularly for the field of computing/communication, nanolasers have become an intriguing area of research as photonic integrated circuits (PICs) of the future would require nanoscale light sources. To that end, nanolasers based on a variety of architectures and underlying physics have been demonstrated in the literature. Metallo-dielectric nanolasers (MDNLs) are particularly attractive since they combine the advantages of ultrasmall footprints and low thresholds offered by other nanolaser types while still offering electromagnetic isolation, telecom-band operation and current injection. In this dissertation, we mainly focus on exploring additional attributes of MDNLs that further lend credence to their suitability for dense integration on-chip. One of these desirable traits we study includes reversible wavelength tuning (upto 8.35 nm) and intensity modulation of an MDNL based on an external electric field (Chapter 2). More importantly, we report that this electric-field based intensity modulation can be performed at high-speeds of upto 400 MHz (limited only by the detector bandwidth). A second characteristic appropriate for dense integration involves investigating the presence of coupling when two MDNLs are designed in proximity on-chip (Chapter 3). Our results indicate that not only does coupling occur, but it can also be inhibited if independent operation of the emitters is required. We further explore the concept of coupling but with regards to phase-locking two high-b, laterally coupled lasers (Chapter 4). We found that high b values, that are usually only exhibited in nanolasers such as MDNLs, help significantly increase the stable phase-locking regions for two coupled lasers. Additionally, high b can also lead to a wider range of phase differences attainable for a

Nearly half a century ago, the German physicist Hermann Haken proved that the laser dynamics could be described, under certain conditions, by the Lorenz equations, the paradigm of deterministic chaos. Unfortunately, its experimental realization has remained elusive for conventional laser materials and cavities mostly due to the extreme pumping conditions and the low cavity quality factors (“bad-cavity condition”) required to achieve Lorenz–Haken (L-H) self-pulsing dynamics upon continuous wave excitation. In this paper, it is theoretically proved that dielectric and plasmonic nanolasers, that can naturally fulfill the bad-cavity condition, may overcome the limitations of macroscopic cavities and make the observation of L-H instabilities in visible-IR solid-state materials become a reality. Remarkably, the adequate choice of active material and cavity design enables the generation of trains of ultrashort pulses in the sub-ps regime and with MHz–GHz repetition rates without the need of resorting to neither mode-locking nor Q-switching techniques. Thus, the results reported in this manuscript unveil a new paradigm in the generation of ultrashort pulses at the nanoscale.

A new approach for analytically solving quantum nonlinear Langevin equations is proposed and applied to calculations of spectra of superradiant lasers where collective effects play an important role. We calculate lasing spectra for arbitrary pump rates and recover well-known results such as the pump dependence of the laser linewidth across the threshold region. We predict new sideband peaks in the spectrum of superradiant lasers with large relaxation oscillations as well as new nonlinear structures in the lasing spectra for weak pump rates. Our approach sheds new light on the importance of population fluctuations in the narrowing of the laser linewidth, in the structure of the lasing spectrum, and in the transition to coherent operation.

Photonic crystal cavities enable strong light–matter interactions, with numerous applications, such as ultra-small and energy-efficient semiconductor lasers, enhanced nonlinearities and single-photon sources. This paper reviews the properties of the modes of photonic crystal cavities, with a special focus on line-defect cavities. In particular, it is shown how the fundamental resonant mode in line-defect cavities gradually turns from Fabry–Perot-like to distributed-feedback-like with increasing cavity size. This peculiar behavior is directly traced back to the properties of the guided Bloch modes. Photonic crystal cavities based on Fano interference are also covered. This type of cavity is realized through coupling of a line-defect waveguide with an adjacent nanocavity, with applications to Fano lasers and optical switches. Finally, emerging cavities for extreme dielectric confinement are covered. These cavities promise extremely strong light–matter interactions by realizing deep sub-wavelength mode size while keeping a high quality factor.

Josephson effects are commonly studied in quantum systems in which dissipation or noise can be neglected or do not play a crucial role. In contrast, here we discuss a setup where dissipative interactions do amplify a photonic Josephson current, opening a doorway to dissipation-enhanced sensitivity of quantum-optical interferometry devices. In particular, we study two coupled nanolasers subjected to phase coherent drivings and coupled by a coherent photon tunneling process. We describe this system by means of a Fokker–Planck equation and show that it exhibits an interesting non-equilibrium phase diagram as a function of the coherent coupling between nanolasers. As we increase that coupling, we find a non-equilibrium phase transition between a phase-locked (PL) and a non-phase-locked (NPL) steady-state, in which phase coherence is destroyed by the photon tunneling process. In the coherent, PL regime, an imbalanced photon number population appears if there is a phase difference between the nanolasers, which appears in the steady-state as a result of the competition between competing local dissipative dynamics and the Josephson photo-current. The latter is amplified for large incoherent pumping rates and it is also enchanced close to the lasing phase transition. We show that the Josephson photocurrent can be used to measure optical phase differences. In the quantum limit, the accuracy of the two nanolaser interferometer grows with the square of the photon number and, thus, it can be enhanced by increasing the rate of incoherent pumping of photons into the nanolasers.

Here we experimentally characterize photonic crystal nanolasers where the first endhole of the mirror has been systamatically shifted. FDTD simulations of similar passive cavities are done in order to find the expected evolution of the quality factor. We find that the predicted increase in the quality factor of the equivalent passive cavities leads to a decrease in the threshold power of the active nanolasers as expected. The maximum output power for varying endhole shifts has also been investigated and shifting the holes to optimize quality factor leads to lower maximum output power, when measuring from the top. The mirror of the photonic crystal cavity is further investigated as the mirror phase and penetration depth into the mirror are determined as a function of the endhole shift.

Nanoscale semiconductor lasers have been developed recently using either metal, metallo-dielectric, or photonic crystal nanocavities. While the technology of nanolasers is steadily being deployed, their expected performance for on-chip optical interconnects is still largely unknown due to a limited understanding of some of their key features. Specifically, as the cavity size is reduced with respect to the emission wavelength, the stimulated and the spontaneous emission rates are modified, which is known as the Purcell effect in the context of cavity quantum electrodynamics. This effect is expected to have a major impact in the 'threshold-less' behavior of nanolasers and in their modulation speed; but its role is poorly understood in practical laser structures, characterized by significant homogeneous and inhomogeneous broadening and by a complex spatial distribution of the active material and cavity field. In this paper, we investigate the role of the Purcell effect in the stimulated and spontaneous emission rates of semiconductor lasers taking into account the carriers' spatial distribution in the volume of the active region over a wide range of cavity dimensions and emitter/cavity linewidths, enabling the detailed modeling of the static and dynamic characteristics of either micro-or nano-scale lasers using single-mode rate-equations analysis. The ultimate limits of scaling down these nanoscale light sources in terms of Purcell enhancement and modulation speed are also discussed showing that the ultrafast modulation properties predicted in nanolasers are a direct consequence of the enhancement of the stimulated emission rate via reduction of the mode volume.

Nanoscale semiconductor lasers have been developed recently using either metal, metallo-dielectric, or photonic crystal nanocavities. While the technology of nanolasers is steadily being deployed, their expected performance for on-chip optical interconnects is still largely unknown due to a limited understanding of some of their key features. Specifically, as the cavity size is reduced with respect to the emission wavelength, the stimulated and the spontaneous emission rates are modified, which is known as the Purcell effect in the context of cavity quantum electrodynamics. This effect is expected to have a major impact in the 'threshold-less' behavior of nanolasers and in their modulation speed; but its role is poorly understood in practical laser structures, characterized by significant homogeneous and inhomogeneous broadening and by a complex spatial distribution of the active material and cavity field. In this paper, we investigate the role of the Purcell effect in the stimulated and spontaneous emission rates of semiconductor lasers taking into account the carriers' spatial distribution in the volume of the active region over a wide range of cavity dimensions and emitter/cavity linewidths, enabling the detailed modeling of the static and dynamic characteristics of either micro-or nano-scale lasers using single-mode rate-equations analysis. The ultimate limits of scaling down these nanoscale light sources in terms of Purcell enhancement and modulation speed are also discussed showing that the ultrafast modulation properties predicted in nanolasers are a direct consequence of the enhancement of the stimulated emission rate via reduction of the mode volume.

Below we highlight the most important breakthroughs and developments accomplished within this 5-year long MURI project (for a more detailed list see the annual reports): *Negative-index metamaterials in the optical range, from near-IR to the visible have been demonstrated. *Negative-index metamaterial with gain completely compensating losses has been demonstrated in the visible (red) part of the spectrum. *Bulk 3D metamaterials with negative refraction have been developed. *Negative refraction in semiconductor based metamaterials has been shown. *Artificial metamagnetics across the entire visible part of the spectrum have been experimentally shown. *World's smallest SPASER-based nanolaser has been demonstrated *Nanolaser based on the hybrid gap mode confining light between a semiconductor amplifying nanostructure and a metal has been demonstrated *Theoretical prediction and experimental realization of magnifying far-field hyperlens *The carpet-cloak has been experimentally realized *Tunable magnetic metamaterials have been demonstrated. We have demonstrated by theories and experiments that nonlinear and electro-optical liquid crystals may be applied in enabling tuning capabilities to metamaterials over a very broad spectral regime from the visible to the infrared. We showed that by using laser induced order parameter as a means of modifying the nematic birefringence, the switching processes can be realized at microseconds nanoseconds speed. *We have designed, developed, and experimentally demonstrated several novel optical switching and modulation photonics devices based on liquid crystals infiltrated nano-plasmonic structures, where the laser induced plasmonic near fields, in conjunction with applied ac field give rise to novel optical switching, transmission and filtering operations that are not possible in passive plasmonic structures.

The most significant accomplishments in this project are: (a) the demonstration of optically pumped silicon based light emitters utilizing colloidal PbSe QD which are inserted in PC microcavities for efficient coupling. Enhancements of spontaneous emission with a linewidth of-2.0 run, corresponding to a cavity Q factor of 775, is observed at 1550 nm at room temperature; (b) an electrically injected silicon based light source using PbSe QDs, which are more compact and versatile. With a current density of 113 mA/cm2, a resonance at X=1669 nm having a linewidth of 4nm is observed, which corresponds to a cavity Q factor of-420. This nanoscale light source based on silicon, which is capable of being fabricated on CMOS chips, is of interest as a practical technology for optical interconnects in silicon photonics; (c) the demonstration of possibility of surface Plasmon enabled nanolaser with round-trip gain in the sense that the transmission in the waveguide increases as the pumping power increases., The original document contains color images. All DTIC reproductions will be in black and white.