Miniature fiber-optic multiphoton microscopy system using frequency-doubled femtosecond Er-doped fiber laser
L. Huang, A. K. Mills, Y. Zhao, D. J. Jones, and S. Tang
Abstract
We report on a miniature fiber-optic multiphoton microscopy (MPM) system based on a frequency-doubled femtosecond Er-doped fiber laser. The femtosecond pulses from the laser source are delivered to the miniature fiber-optic probe at 1.58 µm wavelength, where a standard single mode fiber is used for delivery without the need of free-space dispersion compensation components. The beam is frequency-doubled inside the probe by a periodically poled MgO:LiNbO3 crystal. Frequency-doubled pulses at 786 nm with a maximum power of 80 mW and a pulsewidth of 150 fs are obtained and applied to excite intrinsic signals from tissues. A MEMS scanner, a miniature objective, and a multimode collection fiber are further used to make the probe compact. The miniature fiber-optic MPM system is highly portable and robust. Ex vivo multiphoton imaging of mammalian skins demonstrates the capability of the system in imaging biological tissues. The results show that the miniature fiber-optic MPM system using frequency-doubled femtosecond fiber laser can potentially bring the MPM imaging for clinical applications.
First Detection and Stabilization of the Carrier Envelope Offset of a Diode-Pumped Mode-Locked Ti : Sapphire Laser
K. Gürel, V. J. Wittwer, S. Hakobyan, S. Schilt, and T. Südmeyer
Abstract
So far, Ti:Sapphire-based frequency comb systems required complex bulk green pump lasers. Here we show that green diode pumping enables compact and cost-efficient femtosecond Ti:Sapphire lasers for coherent octave-spanning supercontinuum generation and frequency comb stabilization.
Synchronized dual-repetition-rate two-color fiber lasers for coherent Raman imaging
C. Kong, X. Wei, T. Huser, K. K. Tsia, and K. K. Y. Wong
Abstract
We demonstrate a passively synchronized two-color pulsed fiber laser with dual repetition rates, 20 MHz for 1.0 mm and 80 MHz for 782 nm. The wavelength tunability of both synchronized pulse sources is also investigated.
M. Odstrcil, P. Baksh, C. Gawith, R. Vrcelj, J. G. Frey, and W. S. Brocklesby
Abstract
Ptychographic Coherent diffractive imaging (PCDI) is a significant advance in imaging allowing the measurement of the full electric field at a sample without use of any imaging optics. So far it has been confined solely to imaging of linear optical responses. In this paper we show that because of the coherence-preserving nature of nonlinear optical interactions, PCDI can be generalised to nonlinear optical imaging. We demonstrate second harmonic generation PCDI, directly revealing phase information about the nonlinear coefficients, and showing the general applicability of PCDI to nonlinear interactions.
Second Harmonic Generation Using a Monolithic, Linearly Polarized Thulium Doped Fiber Laser
M. Ganija, , A. Hemming, et al.
Abstract
We investigate the potential for power scaling of 975 nm cw radiation from frequency doubling a monolithic, polarized thulium fiber laser in a periodically poled non-linear material.
Dual-color deep-tissue three-photon microscopy with a multiband infrared laser
K. Guesmi, L. Abdeladim, S. Tozer, P. Mahou, T. Kumamoto, K. Jurkus, P. Rigaud, K. Loulier, N. Dray, P. Georges, M. Hanna, J. Livet, W. Supatto, E. Beaurepaire & F. Druon
Abstract
Multiphoton microscopy combined with genetically encoded fluorescent indicators is a central tool in biology. Three-photon (3P) microscopy with excitation in the short-wavelength infrared (SWIR) water transparency bands at 1.3 and 1.7 µm opens up new opportunities for deep-tissue imaging. However, novel strategies are needed to enable in-depth multicolor fluorescence imaging and fully develop such an imaging approach. Here, we report on a novel multiband SWIR source that simultaneously emits ultrashort pulses at 1.3 and 1.7 µm that has characteristics optimized for 3P microscopy: sub-70 fs duration, 1.25 MHz repetition rate, and µJ-range pulse energy. In turn, we achieve simultaneous 3P excitation of green fluorescent protein (GFP) and red fluorescent proteins (mRFP, mCherry, tdTomato) along with third-harmonic generation. We demonstrate in-depth dual-color 3P imaging in a fixed mouse brain, chick embryo spinal cord, and live adult zebrafish brain, with an improved signal-to-background ratio compared to multicolor two-photon imaging. This development opens the way towards multiparametric imaging deep within scattering tissues.
Zn-indiffused diced ridge waveguides in MgO:PPLN generating 1 watt 780 nm SHG at 70% efficiency
SAM A. BERRY, LEWIS G. CARPENTER, ALAN C. GRAY, PETER G. R. SMITH, AND CORIN B. E. GAWITH
Abstract
We present a metallic zinc indiffused diced ridge waveguide in magnesium doped periodically poled lithium niobate (MgO:PPLN) capable of generating over 1 W of 780 nm with 70% efficiency. Our 40 mm long waveguide has near circular fundamental mode output with diameter 10.4 μm and insertion loss of -1.17 dB. Using a commercial 2 W EDFA-based system, the SHG output power did not exhibit roll-off at maximum available pump power.
Investigation of PPLN Waveguide Uniformity via Second Harmonic Generation Spectra
Alan C. Gray ; Sam A. Berry ; Lewis G. Carpenter ; James C. Gates ; Peter G. R. Smith ; Corin B. E. Gawith
Abstract
Experimental data collection methods and a corresponding numerical model are presented to investigate the quality of waveguide fabrication in nonlinear optics. The method utilises white light interferometry and standard image recognition techniques to calculate a waveguide propagation constant function. This enables comparison of a numerical second harmonic spectrum in quasi-phasematched materials, such as periodically poled lithium niobate, with the waveguide’s experimental phasematching spectrum. Using the presented method, a 3rd order polynomial fit to waveguide ridge width is demonstrated to be in good agreement with experimental phasematching spectra. The presented technique provides a nondestructive route to discriminate between issues in fabrication steps in nonlinear waveguide design.
Two-photon quantum interference and entanglement at 2.1 um
Shashi Prabhakar, Taylor Shields, Adetunmise C. Dada, Mehdi Ebrahim, Gregor G. Taylor, Dmitry Morozov, Kleanthis Erotokritou, Shigehito Miki, Masahiro Yabuno, Hirotaka Terai, Corin Gawith, Michael Kues, Lucia Caspani, Robert H. Hadfield, Matteo Clerici
Abstract
Quantum-enhanced optical systems operating within the 2- to 2.5-um spectral region have the potential to revolutionize emerging applications in communications, sensing, and metrology. However, to date, sources of entangled photons have been realized mainly in the near-infrared 700- to 1550-nm spectral window. Here, using custom-designed lithium niobate crystals for spontaneous parametric down-conversion and tailored superconducting nanowire single-photon detectors, we demonstrate two-photon interference and polarization-entangled photon pairs at 2090 nm. These results open the 2- to 2.5-um mid-infrared window for the development of optical quantum technologies such as quantum key distribution in next-generation mid-infrared fiber communication systems and future Earth-to-satellite communications.
Zinc-indiffused MgO:PPLN waveguides for blue/UV generation via VECSEL pumping
Alan C. Gray, Jonathan R. C. Woods, Lewis G. Carpenter, Hermann Kahle, Sam A. Berry, Anne C. Tropper, Mircea Guina, Vasilis Apostolopoulos, Peter G. R. Smith, and Corin B. E. Gawith
Abstract
We present the design and characterization of a zinc-indiffused periodically poled lithium-niobate ridge waveguide for second-harmonic generation of _390 nm light from 780 nm. We use a newly developed, broadband near infrared vertical external-cavity surface-emitting laser (VECSEL) to investigate the potential for lower-footprint nonlinear optical pump sources as an alternative to larger commercial laser systems. We demonstrate a VECSEL with an output power of 500 mW, containing an intracavity birefringent filter for spectral narrowing and wavelength selection. In this first demonstration of using a VECSEL to pump a nonlinear waveguide, we present the ability to generate 1mWof_390 nmlight with further potential for increased efficiency and size reduction.
