Two-photon Lasing Research Articles

A Novel Built-in Current Sensor for N-WELL SET Detection

This paper presents and evaluates a new built-in current sensor used to detect n-well single-event transients (SETs) induced by radiation strikes in integrated circuits (IC). A 28 nm bulk CMOS test chip containing the proposed sensor design was irradiated by two-photon absorption lasers. Both simulation and experimental data confirm the validity of the proposed design and demonstrate that it can be used for SET detection in advanced technology nodes. Simulation results also demonstrate that this structure has increased SET detection capability and the capability is more sensitive to voltage and temperature variations when compared to the reference design.

A scheme for two-photon lasing with two coupled flux qubits in circuit quantum electrodynamics**Project supported by the National Fundamental Research Program of China (Grant No. 2011cba00200), the National Natural Science Foundation of China (Grant No. 11274295), and the Doctor Foundation of Education Ministry of China (Grant No. 20113402110059).

We theoretically study the system of a superconducting transmission line resonator coupled to two interacting superconducting flux qubits. It is shown that under certain conditions the resonator mode can be tuned to two-photon resonance between the ground state and the highest excited state while the middle excited states are far-off resonance. Furthermore, we study the steady-state properties of the flux qubits and resonator, such as the photon statistics, the spectrum and squeezing of the resonator, and demonstrate that two-photon laser can be implemented with current experimental technology.

Two-photon lasing by a superconducting qubit

We study the response of a magnetic-field-driven superconducting qubit strongly coupled to a superconducting coplanar waveguide resonator. We observed a strong amplification/damping of a probing signal at different resonance points corresponding to a one and two-photon emission/absorption. The sign of the detuning between the qubit frequency and the probe determines whether amplification or damping is observed. The larger blue detuned driving leads to two-photon lasing while the larger red detuning cools the resonator. Our experimental results are in good agreement with the theoretical model of qubit lasing and cooling at the Rabi frequency.

Low threshold melt-processed two-photon organic surface emitting upconversion lasers

Herein, a low threshold, wavelength-tunable, compact, two-photon pumped upconversion laser is presented. The surface emitting lasers are composed of melt-processed 1,4-bis[2-[4-[N,N-di(p-totyl)amino]phenyl]vinyl]benzene (DADSB) as active media and two designed distributed bragg reflectors. The melting fabrication process is very simple, and the lasing threshold is as low as 150μJcm−2pulse−1, when pumped by a Ti:sapphire amplifier operating at 800nm with a 150fs pulse width. To the best of our knowledge, it is one of the lowest values for two-photon lasers. Lasing from multimode to single-mode oscillation is demonstrated. Tunable single mode oscillation was obtained at wavelength from 514nm to 523nm with a spectral width of less than 0.2nm.

Ultralow-Threshold Two-Photon Pumped Amplified Spontaneous Emission and Lasing from Seeded CdSe/CdS Nanorod Heterostructures

Ultralow-threshold two-photon pumped amplified spontaneous emission (2ASE) and lasing in seeded CdSe/CdS nanodot/nanorod heterostructures is demonstrated for the first time. Such heterostructures allow the independent tunability of the two-photon absorption (2PA) cross-section (σ(2)) through varying the CdS rod size, and that of the emission wavelength through varying the CdSe dot size. With an enhanced σ(2), 2ASE in these heterostructures is achieved with an ultralow threshold fluence of ~1.5 mJ/cm(2), which is as much as one order less than that required for spherical semiconductor NCs. Importantly, by exploiting this unique property of the seeded nanorods exhibiting strong quantum confinement even at relatively large rod sizes, a near reciprocal relation between the 2ASE threshold and the 2PA action cross-section (σ(2)η) (where η is the quantum yield) was found and validated over a wide volume range for II-VI semiconductor nanostructures. Ultrafast optical spectroscopy verified that while the Auger processes in these heterostructures are indeed suppressed, ASE in these samples could also be strongly affected by a fast hole-trapping process to the NR surface states. Lastly, to exemplify the potential of these seeded CdSe/CdS nanodot/nanorod heterostructures as a viable gain media for achieving two-photon lasing, a highly photostable microsphere laser with an ultralow pump threshold is showcased.

A FRET-Facilitated Photoswitching Using an Orange Fluorescent Protein with the Fast Photoconversion Kinetics

Fluorescent proteins photoswitchable with noncytotoxic light irradiation and spectrally distinct from multiple available photoconvertible green-to-red probes are in high demand. We have developed a monomeric fluorescent protein, called PSmOrange2, which is photoswitchable with blue light from an orange (ex./em. at 546 nm/561 nm) to a far-red (ex./em. at 619 nm/651 nm) form. Compared to another orange-to-far-red photoconvertable variant, PSmOrange2 has blue-shifted photoswitching action spectrum, 9-fold higher photoconversion contrast, and up to 10-fold faster photoswitching kinetics. This results in the 4-fold more PSmOrange2 molecules being photoconverted in mammalian cells. Compared to common orange fluorescent proteins, such as mOrange, the orange form of PSmOrange has substantially higher photostability allowing its use in multicolor imaging applications to track dynamics of multiple populations of intracellular objects. The PSmOrange2 photochemical properties allow its efficient photoswitching with common two-photon lasers and, moreover, via Förster resonance energy transfer (FRET) from green fluorescent donors. We have termed the latter effect a FRET-facilitated photoswitching and demonstrated it using several sets of interacting proteins. The enhanced photoswitching properties of PSmOrange2 make it a superior photoconvertable protein tag for flow cytometry, conventional microscopy, and two-photon imaging of live cells.

Frequency up-converted lasing in polymeric composites with two-photon absorbing antenna

Energy-transfer-coupled polymeric composites with donors of two-absorbing dyes and acceptors of polymer gain medium are introduced for up-converted laser applications. The two-photon pumped hybrid polymer lasers show significant performance improvement with nearly 10 times reduction of lasing threshold and over 100 times extension of lifespan.

Inhibition and enhancement of two-photon absorption in a four-level inverted-Y semiconductor quantum well system

We theoretically investigate the features of two-photon absorption in a four-level inverted-Y quantum well system. We find that not only the strengths of applied laser fields but also the total closed interaction phase can affect the two-photon absorption dramatically, which can be used to suppress or enhance two-photon absorption. More importantly, the double electromagnetically induced two-photon transparency can be achieved in this system. Thus, it may provide some new possibilities for technological applications in the two-photon lasing, the pulse propagation, and the two-photon entanglement in solid-state quantum information processing.

Two-photon lasing by a single quantum dot in a high-Qmicrocavity

We investigate theoretically two-photon processes in a microcavity containing one quantum dot in the strong coupling regime. The cavity mode can be tuned to resonantly drive the two-photon transition between the ground and the biexciton states, while the exciton states are far-off resonance due to the biexciton binding energy. We study the steady state of the quantum dot and cavity field in presence of a continuous incoherent pumping. We identify the regime where the system acts as two-photon emitter and discuss the feasibility and performance of realistic single quantum dot devices for two-photon lasing.

Frequency upconverted lasing of nanocrystal quantum dots in microbeads

Stable, frequency upconverted lasing of semiconductor nanocrystal quantum dots was demonstrated in silica microbeads under two-photon pumping conditions. Upon infrared excitation, the stimulated emission of the nanocrystal-doped microbeads exhibits sharp peaks at λ∼610 nm with narrow line widths of ≤1 nm. The lasing action has been attributed to the biexciton gain coupled to the whispering gallery modes in spherical cavities, as confirmed by time-resolved photoluminescence spectra. The lasing lifetime characterized in term of pulse numbers (∼106 pulses) was two orders of magnitude longer than that of the dye salt-based two-photon lasers.

Electrically Induced Two-Photon Transparency in Semiconductor Quantum Wells

We demonstrate experimentally two-photon transparency, achieved by current injection into a semiconductor quantum-well structure which exhibits two-photon emission. The two-photon induced luminescence is progressively reduced by the injected current, reaching the point of two-photon transparency-a necessary condition for semiconductor two-photon gain and lasing. These results agree with our calculations.

Low-threshold two-photon pumped ZnO nanowire lasers

We report in this communication the two-photon absorption (TPA)-induced room-temperature lasing performance of ZnO nanowires. Under femtosecond pulse-excitation at lambda = 700 nm in the infrared regime, a remarkably low threshold of 160 microJ/cm(2) was observed for the TPA-induced lasing action, which is of the same order of magnitude as that measured for the linear lasing process. Time-resolved photoluminescence characterization of two-photon pumped ZnO nanowires reveals the presence of a fast decay (3-4 ps) in the stimulated emission as compared to the slow decay (50-70 ps) for the spontaneous emission. The TPA process in ZnO nanowires was characterized with the nonlinear transmission measurement, which uncovers an enhanced TPA coefficient, about 14.7 times larger than that of bulk ZnO samples. The observed TPA enhancement in ZnO nanowires accounts for the low threshold lasing behavior, and has been attributed to the intensified optical field confined within the nanowire waveguides.

Two-photon absorption and lasing properties of new fluorene derivatives

Linear photophysical properties, two-photon absorption (2PA), and lasing effects of new fluorene derivatives, 2,7-bis(4-(phenylthio)styryl)-9,9-didecyl-9H-fluorene (1) and 2,7-bis(4-(phenylsulfonyl)styryl)-9,9-didecyl-9H-fluorene (2), have been investigated. The relatively strong solvatochromic behavior of symmetrical compounds 1 and 2 can be explained by the phenomenon of symmetry breaking in the electronic distribution of the first excited state. The 2PA spectra of 1 and 2 were obtained over a broad spectral range (480–880 nm) by two-photon-induced fluorescence and open aperture Z-scan methods, in which excited state absorption and stimulated emission processes were considered in the fitting procedure. Maximum values of 2PA cross-sections ∼1300–1900 GM were obtained for 1 and 2 in the two-photon-allowed absorption bands at ∼660 nm. Efficient lasing of 1 and 2 was demonstrated in a nondispersive flat resonator with picosecond transverse pumping at 355 nm. Lasing efficiencies were ∼25–30% in this resonator, and independent of solvent.

Two‐Photon Absorption and Lasing in First‐Generation Bisfluorene Dendrimers

The two-photon absorption properties of bisfluorene dendrimers are investigated in both the nanosecond and the femtosecond regime. By substituting different dendrons onto the same chromophore (see figure), we examine the effect of the dendrons on the spectrum and magnitude of the two-photon absorption. As these dendrimers have high photoluminescence quantum yields, we then proceed to make two-photon pumped dendrimer lasers.

Evolution of emmitted light intensity in two-photon pumping random lasers

Based on the diffusive equation of incoherent-feedback random lasers，whose gain is modified by adding a saturation factor，the evolution of the emitted light intensity in two-photon pumping random lasers varying with time is studied by use of finite difference method. Numerical results show how the intensity of emitted light varies from the spontaneous radiation，which undergoes amplification at small-signal gain，to the steady output due to the saturation effect. It is noted that the nonlinear effect，e.g. saturation of gain，in such laser system can be achieved under low intensity conditions due to the disorder of media. Our results give a theoretical support to obtaining the steady output of the two-photon pumping random lasers.

Dynamics of Two-Photon Lasers with Λ AtomicLevel Configuration

We derive the dimensionless dynamic equations of two-photonlasers with Λ atomic level configuration by using the quantumLangevin equation method with the considerations of atomic coherenceand injected classical fields. Then we analyze the stability and thechaotic dynamics of the two-photon laser by calculating thebifurcation diagram and the maximum Lyapunov exponent (MLE). Ourresults show that the Lorenz strange attractors and one-focusstrange attractors can exist in this system, and the chaos can beinduced or inhibited by the injected classical fields viaHopf-bifurcations or crises, while the atomic coherence induceschaos via crises, and inhibit chaos via Hopf bifurcation orcrises.

Theoretical Investigation on the Saturation Effects in Two-photon Pumping Random Lasers

A numerical analysis of the saturation effects of emitted light intensity in two-photon pumping random lasers is presented by adding the saturation item to modify the gain in the diffusive equation. Numerical results show that the emitted intensity reaches its saturation value in a short time interval with sufficient pumping. From the analysis of normalized emitted intensity and saturation intensity, one can obtain a method to control steady output intensity of two-photon pumping random lasing by adjusting some parameters of the random media

Two-photon lasing stimulated by collective modes

Considering the resonator losses in photon pairs the coherence between the photon pairs as the function of number of bimodes is studied. Taking into account the big number of resonator bimodes in which the photon pairs with fixed energy and phase are generated, it is demonstrated that the coherence between the pairs of photons remains larger than the coherence between individual photons. It is shown that the ignition of two-photon lasing from vacuum fluctuations increases with the increase in the number of resonator modes. This effect can be regarded as a collective phenomenon between the resonator bimodes in which the pairs of entangled photons are generated.

Two-Photon Lasers Based on Intersubband Transitions in Semiconductor Quantum Wells

We propose to make a two-photon laser based on intersubband (sublevel) transitions in semiconductor nanostructures. The advantages and feasibility of such a two-photon laser are analyzed in detail using the density matrix approach. Both one-photon and two-photon gains in a three subband quantum well structure are studied on the same footing to show how the two-photon gain can be maximized, while the competing one-photon gain is minimized. The results show that a sufficient two-photon gain can be achieved to overcome one-photon competition and the loss of a conventional semiconductor cavity, making intersubband transitions one of the very few feasible approaches to two-photon lasing.

Two-photon absorption and lasing due to biexciton in CuCl quantum dots

We have demonstrated laser emission in CuCl quantum dots embedded in NaCl matrix by direct creation of biexcitons through two-photon absorption process. Mode distance and emitting direction of laser emission show that cavity is composed of cleaved surfaces of the matrix. In addition, we confirmed that the lasing originated from the biexciton state by taking account of the polarization selection rule of the lowest biexciton state. It is suggested that two-photon excitation of the biexcitons is very useful for high-efficient lasing in quantum dots.