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1.
Appl Opt ; 63(10): 2561, 2024 Apr 01.
Article in English | MEDLINE | ID: mdl-38568536

ABSTRACT

This erratum corrects errors in Fig. 4(b) of the original paper, Appl. Opt.63, 1847 (2023)APOPAI0003-693510.1364/AO.510265. This correction does not affect any of the results or conclusions of the aforementioned paper.

2.
Appl Opt ; 63(7): 1847-1853, 2024 Mar 01.
Article in English | MEDLINE | ID: mdl-38437289

ABSTRACT

A method called the optimal demodulated Lorentzian spectrum is employed to precisely quantify the narrowness of a laser's linewidth. This technique relies on the coherent envelope demodulation of a spectrum obtained through short delayed self-heterodyne interferometry. Specifically, we exploit the periodic features within the coherence envelope spectrum to ascertain the delay time of the optical fiber. Furthermore, the disparity in contrast within the coherence envelope spectrum serves as a basis for estimating the laser's linewidth. By creating a plot of the coefficient of determination for the demodulated Lorentzian spectrum fitting in relation to the estimated linewidth values, we identify the existence of an optimal Lorentzian spectrum. The corresponding laser linewidth found closest to the true value is deemed optimal. This method holds particular significance for accurately measuring the linewidth of lasers characterized as narrow or ultranarrow.

3.
Appl Opt ; 62(27): 7169-7174, 2023 Sep 20.
Article in English | MEDLINE | ID: mdl-37855572

ABSTRACT

We demonstrate a simple, low-cost, and well-performing optical phase-locked loop (OPLL) circuit with ADF4007 as the phase frequency detector chip to achieve frequency and phase locking of two semiconductor lasers in both short and long terms. The measured short term performances, determined by fast feedback, show that the spectral width of the beat signal is low, around 1 Hz, and the residual phasing error is 0.04r a d 2. The measured long term performances, determined by slow feedback, show that the drift of the central frequency of the beat signal is within 1.1(1) Hz in 2 h, and the derived Allan deviation is less than 0.4 Hz within all integration times of up to 1000 s. The phase noise measurement shows a suppression of phase noise of the beat signal from free running to closed-loop OPLLs in a Fourier frequency of 10 Hz-20 kHz. These measurements show that the OPLL circuit we modified can fit most scientific experiments requiring a fixed frequency difference and phase coherence.

4.
Opt Express ; 30(25): 44434-44448, 2022 Dec 05.
Article in English | MEDLINE | ID: mdl-36522868

ABSTRACT

A new theory for the low coherence laser amplification in rare ions doped glass has been proposed. Based on one-dimensional continuous energy level assumption and independent response assumption, the theory can describe the amplification of low coherence laser pulses with any time scale and any bandwidth. By the new theory, McCumber formula can be obtained, and a complete low coherence optical pulse amplification model in neodymium glass is established. Computation shows that at high fluences, inhomogeneous broadening will severely limit energy extraction of narrowband high coherence laser, therefore the extraction of broadband low coherence laser will exceed that of narrowband high coherence laser. In addition, the portion of long-wave of the output spectrum is slightly larger than that predicted by the homogeneous model. The new theory could be beneficial for the studies of low coherence pulse amplification in rare earth doped medium and other laser mediums.

5.
Opt Express ; 30(12): 21906-21917, 2022 Jun 06.
Article in English | MEDLINE | ID: mdl-36224901

ABSTRACT

We propose a random polarization smoothing method for low-coherence laser to obtain focal spot with random polarization that evolves rapidly in sub-picosecond timescales. Random polarization smoothing is realized by a half-aperture wave plate with sufficient thickness. The degree of polarization and polarization evolution of the focal spot are studied theoretically. The calculation results show that random polarization smoothing can make the polarization of focal spot evolve rapidly and randomly in time and space. Experimentally, the polarization of the focal spot of low-coherence laser with random polarization smoothing is measured by a single-shot polarimeter. The measurement results show that the degree of polarization of the focal spot is reduced to 0.22 on average, which proves the effectiveness of random polarization smoothing. The random polarization smoothing technique on low-coherence laser is expected to reduce the laser plasmas instability through its multi-dimensional random evolution properties.

6.
Opt Express ; 30(20): 35567-35579, 2022 Sep 26.
Article in English | MEDLINE | ID: mdl-36258505

ABSTRACT

Two new random polarization smoothing methods using full-aperture elements are proposed on low-coherence lasers, one using birefringent wedge and one using flat birefringent plate. By designing the crystal axis direction and wedge angle of the birefringent plates, the methods can selectively introduce time delay and spatial displacement, so as to obtain fast random evolution of transient polarization by utilizing low spatiotemporal coherence of the laser focal field. Both methods avoid the near field discontinuity and can be used under high fluence. The method using birefringent wedge can slightly improve focal spot uniformity, and the method using flat birefringent plate can obtain non-polarization with DOP lower than 2%. Theoretical studies show that the resulting focal polarization evolves rapidly on sub-picosecond timescales and rapidly covers the entire Poincaré sphere. The method using birefringent wedge is achieved in experiment. The results show that the degree of polarization of the focal spot is reduced from 1 to 0.27, which proves the effectiveness of the full-aperture random polarization smoothing. The full-aperture random polarization smoothing can generate a focal field very close to unpolarized thermal light, which is expected to suppress the laser plasmas instability.

7.
Angew Chem Int Ed Engl ; 61(11): e202116681, 2022 Mar 07.
Article in English | MEDLINE | ID: mdl-35044716

ABSTRACT

The emitting layer based on a host-guest system plays a crucial role in organic light-emitting diodes (OLEDs). While emitters have witnessed rapid progress in structural diversity, hosts still rely heavily on traditional structures and are underdeveloped. Herein a "medium-ring" strategy has been put forward to design structurally nontraditional host molecules, which are not only rotatable enough to suppress close π-π stacking, thus reducing exciton annihilation, but also rigid enough to prevent excessive conformational flipping, thus inhibiting non-radiative decay. Accordingly, a brand-new type of bipolar hosts with a twisted "butterfly-shaped heptagonal acceptor (EtBP), which features an electron-deficient benzophenone fragment with a flexible ethylidene bridge, has been developed. With satisfactory morphological stability and well-balanced hole- and electron-transporting properties, the EtBP-based bipolar hosts enable high-performance RGB phosphorescent OLEDs with small efficiency roll-off, which are superior to those of acyclic benzophenone-based devices.

8.
Opt Lett ; 45(24): 6839-6842, 2020 Dec 15.
Article in English | MEDLINE | ID: mdl-33325909

ABSTRACT

We report the first (to the best of our knowledge) high-power, low-coherence Nd:glass laser delivering kilojoule pulses with a coherent time of 249 fs and a bandwidth of 13 nm, achieving the 63%-efficiency second-harmonic conversion of the large-aperture low-coherence pulse and good beam smoothing effect. It provides a new type of laser driver for laser plasma interaction and high energy density physics research.

9.
Appl Opt ; 59(10): 2976-2982, 2020 Apr 01.
Article in English | MEDLINE | ID: mdl-32400574

ABSTRACT

The smoothing effect of induced spatial incoherence combined with a lens array on a large-bandwidth and short-coherence-time laser is reported. A theoretical model based on statistical optics is developed to describe the spatial and temporal characteristics of the focal spot. Theoretical simulation is consistent with the experimental results. A method was proposed to remove or reduce the residual interference fringes of the experimental focal spot, and both the simulation and analysis show that this method does not affect the smoothing speed of the focal spot.

10.
Chem Sci ; 12(7): 2419-2426, 2020 Dec 08.
Article in English | MEDLINE | ID: mdl-34164007

ABSTRACT

Molecular engineering enabling reversible transformation between helical and planar conformations is described herein. Starting from easily available 2-(pyridin-2-yl)anilines and alkynes, a one-pot strategy is set up for the synthesis of aza[4]helicenes via two successive rhodium-catalyzed C-H activation/cyclizations. Helical pyrrolophenanthridiziniums can be transformed into planar conformations through the cleavage of acidic pyrrole N-H, leading to turn-off fluorescence. NMR spectra, single crystal X-ray diffraction and DFT calculations demonstrate that the formation of an intramolecular C-H⋯N hydrogen bond is beneficial to stabilize the pyrrole nitrogen anion of the planar molecule and provide increased planarity. The reversible conformation transformations can be finely adjusted by the electron-donating and -withdrawing groups on the π+-fused pyrrole skeleton in the physiological pH range, thus affording an opportunity for pH-controlled intracellular selective fluorescence imaging. Pyrrolophenanthridiziniums show turn-on fluorescence in lysosomes owing to the acidic environment of lysosomes and turn-off fluorescence out of lysosomes, indicating the occurrence of the deprotonation reaction outside lysosomes and the corresponding transformation from helical to planar conformations.

11.
Opt Lett ; 44(17): 4359-4362, 2019 Sep 01.
Article in English | MEDLINE | ID: mdl-31465402

ABSTRACT

The nonlinear frequency conversion of low-temporal-coherent light holds a variety of applications and has attracted considerable interest. However, its physical mechanism remains relatively unexplored, and the conversion efficiency and bandwidth are extremely insufficient. Here, considering the instantaneous broadband characteristics, we establish a model of second-harmonic generation (SHG) of a low-temporal-coherent pulse and reveal its differences from the coherent conditions. It is found that the second-harmonic spectrum distribution is proportional to the self-convolution of that of a fundamental wave. Because of this, we propose a method for realizing low-temporal-coherent SHG with high efficiency and broad bandwidth, and experimentally demonstrate a conversion efficiency up to 70% with a bandwidth of 3.1 THz (2.9 nm centered at 528 nm). To the best of our knowledge, this is the highest efficiency and broadest bandwidth of low-temporal-coherent SHG to date. Our research opens the door for the study of low-coherent nonlinear optical processes.

12.
Appl Opt ; 58(8): 2121-2126, 2019 Mar 10.
Article in English | MEDLINE | ID: mdl-30874076

ABSTRACT

The smoothing scheme combining a diffraction-weakened lens array with the induced spatial incoherence method is proposed and demonstrated to be an efficient smoothing scheme for broadband laser systems. In our simulation, the RMS illumination nonuniformity of the target spot is reduced to 2% after sufficient smoothing time. The temporal characteristics and spatial power spectral density of the scheme are theoretically analyzed. When the incident light has intensity fluctuations, the uniformity of the target spot is stable, which means a robust smoothing scheme, and which predicts practical applications to the smoothing of broadband laser systems.

13.
Org Lett ; 21(4): 1037-1041, 2019 02 15.
Article in English | MEDLINE | ID: mdl-30681876

ABSTRACT

Disclosed herein is a highly efficient strategy to fuse an aromatic ring to azoarenes for one-pot access to 5,6-phenanthrolinium skeletons via tandem ortho-C-H arylation and aryl quaternization. This protocol enables ortho-hindered azobenzenes to solely form 5-aryl-5,6-phenanthroliniums and ortho-unhindered azobenzenes to exclusively generate 5,7-diaryl-5,6-phenanthroliniums. The diarylated products (5k-5r) exhibit far-red to NIR emissions (678-742 nm) with large Stokes shifts, can specifically light up mitochondria in living cells, and, moreover, possess excellent photostability and low cytotoxicity.


Subject(s)
Azo Compounds/chemistry , Fluorescent Dyes/chemistry , Hydrocarbons, Aromatic/chemistry , Mitochondria/drug effects , Phenanthrolines/pharmacokinetics , Infrared Rays , Molecular Structure , Phenanthrolines/chemical synthesis , Phenanthrolines/chemistry
14.
Appl Opt ; 55(35): 10124-10132, 2016 Dec 10.
Article in English | MEDLINE | ID: mdl-27958424

ABSTRACT

Based on the premise that further improvements to the size and damage threshold of large-aperture optical components are severely limited, coherent beam combining (CBC) is a promising way to scale up the available peak power of pulses for ultrashort ultrahigh intensity laser systems. Spectral phase effects are important issues and have a significant impact on the performance of CBC. In this work, we analyze systematically factors such as spectral dispersions and longitudinal chromatism, and get the general spectral phase control requirements of CBC for ultrashort ultrahigh intensity laser systems. It is demonstrated that different orders of dispersion influence intensity shape of the combined beam, and high-order dispersions affect the temporal contrast of the combined beam, while the number of the channels to be combined has little impact on the temporal Strehl ratio (SR) of the combined beam. In addition, longitudinal chromatism should be controlled effectively since it has a detrimental effect on the combined beam at the focal plane, both temporally and spatially.

15.
Appl Opt ; 54(33): 9939-48, 2015 Nov 20.
Article in English | MEDLINE | ID: mdl-26836561

ABSTRACT

Large-aperture ultrashort ultrahigh intensity laser systems are able to achieve unprecedented super-high peak power. However, output power from a single laser channel is not high enough for some important applications and it is difficult to improve output power from a single laser channel significantly in the near future. Coherent beam combining is a promising method which combines many laser channels to obtain much higher peak power than a single channel. In this work, phase effects of coherent beam combining for large-aperture ultrashort laser systems are investigated theoretically. A series of numerical simulations are presented to obtain the requirements of spatial phase for specific goals and the changing trends of requirements for different pulse durations and number of channels. The influence of wavefront distortion on coherent beam combining is also discussed. Some advice is proposed for improving the performance of combining. In total, this work could help to design a practical large-aperture ultrashort ultrahigh intensity laser system in the future.

16.
Appl Opt ; 52(4): 718-25, 2013 Feb 01.
Article in English | MEDLINE | ID: mdl-23385912

ABSTRACT

Object image grating self-tiling reduces difficulties of obtaining an ideal grating tiling condition by eliminating three tiling errors in six within a tiled grating. However, this may bring two potential problems: higher requirements of adjustment accuracy and maintaining stability. To examine the application values of this grating tiling configuration, the performance of object image grating self-tiling and traditional grating tiling configurations on accuracy and stability are compared theoretically and experimentally. Adjustment accuracy requirements of two grating tiling configurations are calculated, a comparative experiment of long-term stabilities is demonstrated, and relevant theoretical simulation analyses are developed to explain the experiment results.

17.
Appl Opt ; 51(15): 2941-50, 2012 May 20.
Article in English | MEDLINE | ID: mdl-22614597

ABSTRACT

Aiming at getting the general requirements of the beam combine for ignition scale laser facilities, the analytical expressions including the factors affecting the combine results are derived. The physical meanings of every part are illustrated. Based on these expressions, the effects of the factors, including the beam configuration, piston error, and tip/tilt error, are studied analytically and numerically. The results show that the beam configuration cannot affect the Strehl ratio (SR) of the combined beam, but it influences the FWHM of the main peak and the ratio of the main peak and the side peak. The beam separation should be no more than 1.24 times the individual beam width for the multibeam combine, and be close to the individual beam width for the two-beam combine as much as possible. The piston error can change the characteristics of the combine beam focus, including the peak intensity, the focal spot morphology, the fractional energy contained within a certain area, and the center of mass. For the two-beam combine, a piston error less than 2π/5 rad is suitable, and for the multibeam combine, the standard deviation of the piston error should be no more than 2π/10 rad. The tip/tilt error has a great influence on the combined results. It affects the superposition degree of the focal spots of the combined elements directly. A requirement of 0.5~1 µrad for the standard deviation of the tip/tilt error is adequate.

18.
Appl Opt ; 50(20): 3609-14, 2011 Jul 10.
Article in English | MEDLINE | ID: mdl-21743573

ABSTRACT

FM-to-AM conversion in the ninth beam of the Shen Guang II laser system with sinusoidal phase-modulated spectra is calculated and analyzed. The simulations show that the intensity modulation at 3ω is much more serious compared to the other wavebands and it is mostly induced by the frequency conversion system rather than the amplification chain. The compensation effects of FM-to-AM conversion in the frequency conversion system by angular dispersion grating and cascaded crystals are numerically simulated and compared. Compared to the cascaded crystals, the angular dispersion grating could maintain higher frequency conversion efficiency with wide spectral width and offer a higher dynamic range of compensation effectiveness versus fundamental laser intensity. Combined with a precompensation filter before the amplification chain, FM-to-AM conversion at 3ω could be eliminated.

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