Sensitivity enhancement of fiber-laser-based stimulated Raman scattering microscopy by collinear balanced detection technique
K. Nose, Y. Ozeki, T. Kishi, K. Sumimura, N. Nishizawa, K. Fukui, Y. Kanematsu, and K. Itoh
Abstract
We propose the collinear balanced detection (CBD) technique for noise suppression in fiber laser (FL)-based stimulated Raman scattering (SRS) microscopy. This technique reduces the effect of laser intensity noise at a specific frequency by means of pulse splitting and recombination with a time delay difference. We experimentally confirm that CBD can suppress the intensity noise of second harmonic (SH) of Er-FL pulses by 13dB.The measured noise level including the thermal noise is higher by only 1.4 dB than the shot noise limit. To demonstrate SRS imaging, we use 4-ps SH pulses and 3-ps Yb-FL pulses, which are synchronized subharmonically with a jitter of 227 fs. The effectiveness of the CBD technique is confirmed through SRS imaging of a cultured HeLa cell.
Generation of 43 W of quasi-continuous 780 nm laser light via high-efficiency, single-pass frequency doubling in periodically poled lithium niobate crystals
S. Chiow, T. Kovachy, J. M. Hogan, and M. A. Kasevich
Abstract
We demonstrate high-efficiency frequency doubling of the combined output of two 1560 nm 30 W fiber amplifiers via single pass through periodically poled lithium niobate (PPLN) crystals. The temporal profile of the 780 nm output is controlled by adjusting the relative phase between the seeds of the amplifiers. We obtain a peak power of 34W of 780 nm light by passing the combined output through one PPLN crystal, and a peak power of 43 W by passing through two cascading PPLN crystals. This source provides high optical power, excellent beam quality and spectral purity, and agile frequency and amplitude control in a simple and compact setup, which is ideal for applications such as atom optics using Rb atoms.
Frequency-comb-referenced multi-wavelength profilometry for largely stepped surfaces
S. Hyun, M. Choi, B. J. Chun, S. Kim, S. W. Kim, and Y. J. Kim
Abstract
3-D profiles of discontinuous surfaces patterned with high step structures are measured using four wavelengths generated by phase-locking to the frequency comb of an Er-doped fiber femtosecond laser stabilized to the Rb atomic clock. This frequency-comb-referenced method of multi-wavelength interferometry permits extending the phase non-ambiguity range by a factor of 64,500 while maintaining the sub-wavelength measurement precision of single-wavelength interferometry. Experimental results show a repeatability of 3.13 nm (one-sigma) in measuring step heights of 1800, 500, and 70 μm. The proposed method is accurate enough for the standard calibration of gauge blocks and also fast to be suited for the industrial inspection of microelectronics products.
Narrowband photon pair source for quantum networks
F. Monteiro, a Martin, B. Sanguinetti, H. Zbinden, and R. T. Thew
Abstract
We demonstrate a compact photon pair source based on a periodically poled lithium niobate nonlinear crystal in a short cavity. This approach provides efficient, low-loss, mode selection that is compatible with standard telecommunication networks. Photons with a coherence time of 8.6 ns (116 MHz) are produced and their purity is demonstrated. A source brightness of 134 pairs (s. mW. MHz-1) is reported. The cavity parameters are chosen such that the photon pair modes emitted can be matched to telecom ultra dense wavelength division multiplexing (U-DWDM) channel spacings. The high level of purity and compatibility with standard telecom networks is of great importance for complex quantum communication networks.
N. Bruno, E. Zambrini Cruzeiro, A. Martin, and R. T. Thew
Abstract
We report the realization of a fibred polarization entangled photon-pair source at 1560 nm based on a type-II nonlinear interaction and working in the picosecond regime. By taking advantage of a set of fibre filters, we deterministically separate the photons and project them into wavelength separable states. A standard entanglement measurement with a net interference visibility close to 1 proves the relevance of our approach as an enabling technology for entanglement-based quantum communication.
Distribution of Squeezed States through an Atmospheric Channel
C. Peuntinger, B. Heim, C. R. Müller, C. Gabriel, C. Marquardt, and G. Leuchs
Abstract
Continuous variable quantum states of light are used in quantum information protocols and quantum metrology and known to degrade with loss and added noise. We were able to show the distribution of bright polarization squeezed quantum states of light through an urban freespace channel of 1.6 km length. To measure the squeezed states in this extreme environment, we utilize polarization encoding and a postselection protocol that is taking into account classical side information stemming from the distribution of transmission values. The successful distribution of continuous variable squeezed states is accentuated by a quantum state tomography, allowing for determining the purity of the state.
High-power non linear frequency converted laser diodes fiber laser
O. Jensen, P. Andersen, and A. Hansen
Abstract
We present different methods of generating light in the blue-green spectral range by nonlinear frequency conversion of tapered diode lasers achieving state-of-the-art power levels. In the blue spectral range, we show results using single-pass second harmonic generation (SHG) as well as cavity enhanced sum frequency generation (SFG) with watt-level output powers. SHG and SFG are also demonstrated in the green spectral range as a viable method to generate up to 4 W output power with high efficiency using different configurations.
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.
