Continuum White Light Generation. WhiteLase: High Power Ultrabroadband

Transcription

1 Continuum White Light Generation WhiteLase: High Power Ultrabroadband Light Sources

2 Technology Ultrafast Pulses + Fiber Laser + Non-linear PCF = Spectral broadening from 400nm to 2500nm

3 Ultrafast Fiber Laser MOPA MOPA = Master Oscillator Power Amplifier All fiber design no free-space optics In supercontinuum systems post processing is non-linear microstructured optical fiber (PCF)

4 Master Oscillator Diode pumped Yb fiber laser at 1064nm Passively mode-locked via saturable absorber mirror Self-starting operation providing transform limited pulses 3ps (min) to >100ps (max) Repetition rate set by fiber length: 20MHz (min) to 110MHz (max)

5 Changing Repetition Rate Master Oscillator Pulsepicker Amplifier PCF I I I Repetition Rate 20MHz t Repetition Rate 10MHz t Repetition Rate 6.67MHz (custom) t Repetition Rate 5MHz t Pulse energy 100nJ Pulse energy 100nJ Pulse energy 100nJ Pulse energy 100nJ Average Power 2W pulse-pulse: 50ns Average Power 1W pulse-pulse: 100ns Average Power 667mW pulse-pulse:150ns Average Power 500mW pulse-pulse: 200ns 5

6 Supercontinuum Generation Spectrum related primarily to the Kerr and Raman non-linearities Raman scattering, Self Phase Modulation (SPM) and Four-wave mixing (FWM) involved Pump needs to be close to the zerodispersion of the fiber in the anomalous regime High peak-power is maintained and the fiber non-linearity can be maintained over long interaction lengths Result is spectral broadening in both directions around the pump wavelength

7 Photonic Crystal Fiber (PCF) Microstructured fiber with solid silica core and air/silica cladding High difference in refractive index between core and cladding guides light Single spatial mode at all wavelengths Small core-size enhances non-linear effects Group Velocity Dispersion properties can be carefully designed 7

8 Peak Power Drives Spectral Bandwidth

9 Peak Power Drives Spectral Bandwidth

10 Peak Power Drives Spectral Bandwidth

11 Peak Power Drives Spectral Bandwidth

12 Peak Power Drives Spectral Bandwidth

13 Peak Power Drives Spectral Bandwidth

14 Peak Power Drives Spectral Bandwidth

15 Peak Power Drives Spectral Bandwidth

16 Supercontinuum Laser Evolution Over the last 7 years, SC lasers have seen an order of magnitude increase in their output powers. Market demands and technology developments are driving product evolution in three key directions: Higher power More spectral bandwidth Lower cost / higher reliability W W W 2013 >10W

17 Higher Power Supercontinuum Spectrum is determined by the peak power of pump pulses. By increasing the repetition rate of the oscillator, the supercontinuum power increases while the spectrum is fixed. Current state-of-art SC has >10W average power with >1.5W in the visible range. Short term experiments (200h) performed at much higher powers of 30W (5W visible power) have suggested significant power scaling is still achievable using current technology... 10W laser 1.5W visible

18 Limitations of Supercontinuum Lasers Photodarkening of fibers was historically a problem. Generation of deeper UV wavelengths inside fiber causes photodarkening. Proprietary fiber design can reduce photodarkening and enables SC systems capable of operating at higher power levels and UV wavlengths to a limited extent Further power scaling may involve combining multiple SC sources into a single high power output of reduced brightness. Deeper UV wavelengths can be achieved by harmonically doubling SC output. Reliability of youthful technology.

19 Properties of Supercontinuum Light Broadband pulsed output Typically 2µm bandwidth Continuously bright spectrum with no gaps Laser-like beam propagation Collimated output Can be steered/manipulated like a laser Single spatial mode at all wavelengths Can be efficiently fiber-coupled Can be focused to diffraction-limited spot High brightness compared to other BB sources Ultrafast pulses at high repetition rate Can be used as Quasi-Continuous Wave source Can be used for lifetime study ( 50ps filtered pulse-width) Low temporal coherence can be used for OCT

20 Applications Fluorescence excitation Industrial inspection and sorting Lifetime study Super-resolution techniques Medical illumination Broadband spectroscopy Nanophotonics Optical Coherence Tomography Hyper-spectral measurement Raman spectroscopy High intensity lamp replacement

21 Future Developments UV Supercontinuum High Power <390nm Low Power <350nm Average Power Scaling 10W supercontinuum released in W supercontinuum demonstrated in lab Lower Repetition rates Project to develop single-shot to 80MHz source Femtosecond Supercontinuum Pumping PCF with femtosecond 1064nm laser source

22 Thank you Tim Gerke direct:

23 Fianium WhiteLase WhiteLase micro WhiteLase SC400, SC450 & SC480 ALP (Advanced Laser Platform) Compact mode-locked supercontinuum lasers

24 Spectral power density (dbm/nm) WhiteLase micro Wavelength (nm) Spectrum from <450nm to >2000nm >200mW total output power (>20mW visible) 20MHz repetition rate

25 Spectral Power Density (mw/nm) WhiteLase SC400 & SC450 7 SC SC SC Wavelength (nm)

26 Spectral power desnity (nj/nm) WhiteLase SC450-HE Optimised for maximum supercontinuum pulse energy 1nJ/nm from nm Full Spectrum from <550nm to >1750nm Operates at 1MHz and 0.5MHz user selectable Super-resolution and spectroscopy applications Wavelength (nm)

27 SC390 UV-Enhanced Short-wavelength cut-in <390nm shortest available Long wavelength edge ~2400nm Up to 3W total power

28 Acousto-Optic Tunable Filter AOTF Removable tunable filter compatible with all Fianium WhiteLase Supercontinuum Systems Up to 8 collinear individually tunable channels Three wavelength options covering full spectral range : nm, nm & nm AOTF-DUAL Dual output filter module to cover extended wavelength range Can cover any two standard AOTF wavelength options AOTF-HP New high-power version of Fianium AOTF system Provides >70% of supercontinuum power density to free-space unpolarised beam

29 SuperChrome Tunable Filter Tunable Wavelength Single channel tunable from 400nm to 850nm Broadband White Light setting Tunable Bandwidth <5nm to >50nm FWHM tunability Optimise channel bandwidth vs. output power High Performance Up to 50dB out-of-band suppression 80% transmission Fast 100nm/s tuning speed High beam quality Free-space or FC fiber delivered output