Femtosecond Optical Parametric Amplifier (OPA)

Overview
Specs
Pulse Calculations
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Peter Fendel
Director, Laser Division

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2018 Category of Lasers

Key Specifications
Output Beam	Signal	Idler
Wavelength Range	1275 - 1800 nm	2.4 - 4.4 µm
Pulse Energy (@ 1 MHz)^a	>0.4 μJ	>0.1 μJ
Output Power (Average @ 4 MHz)^a	>1.5 W	>0.25 W
Repetitation Rate (Tunable)	1 - 4 MHz
Support Documents

These specifications are given for the peak of the tuning curve.

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The Y-Fi OPA amplifies a coherently generated white-light seed in a nonlinear crystal, accessing signal wavelengths of 1275 - 1700 nm. The parametric amplification process amplifies the seed and simultaneously generates an idler pulse tunable from 2.4 - 4.4 µm.

Features

Flat Pulse Energy Scaling with Repetition Rate (See Specs Tab)
Tunable Repetition Rate: 1 - 4 MHz
Signal Output Pulse Duration as Short as 80 fs
High Output Power and Pulse Energy (See Key Specifications Table to the Right)
<1.5% Typical Shot-to-Shot Pulse Energy Deviation
Integrated Y-Fi™ Ytterbium Fiber Laser for Increased Stability
By-Pass Port for Access to Full Y-Fi™ HP Fiber Laser Capabilities
Multimode SMA Output Port for Signal Monitoring
Control via Software for Hands-Free Operation (Laptop and Software Included)
Compact Footprint

Applications

Three-Photon Microscopy of Fluorescent Proteins (e.g., GFP, GCaMP, RFP)
- Typical Pulse Energy & Power Scaling for 1330 nm and 1680 nm
  Excitation Wavelengths on Specs Tab
Two-Photon Microscopy of Novel Highly Red-Shifted Fluorescent Tags
NIR and MIR Supercontinuum Generation
Pump-Probe Spectroscopy
Tip-Enhanced MIR Nanoscopy (Nanospectroscopy)

Thorlabs' Y-Fi™ Femtosecond Optical Parametric Amplifier (OPA) with an integrated
Y-Fi™ Ytterbium Fiber Laser converts single frequency light (1035 nm) into a tunable NIR and MIR source by using white light and optical parametric amplification. The Y-Fi OPA is coherently seeded from white-light continuum generated in bulk media by the Y-Fi™ HP fiber laser pulse (see schematic to the right) and features a >15% conversion efficiency that delivers signal and idler outputs in the 1275 - 1800 nm and 2.4 - 4.4 micron range, respectively. With >0.4 µJ pulse energies and a tunable repetition rate from 1 to 4 MHz, the Y-Fi™ OPA facilitates life science applications that require deep imaging depths through the use of three-photon microscopy, as well as high signal-to-noise ratios and minimal phototoxicity. Detailed specifications are available on the Specs tab.

The Y-Fi OPA is designed to be a robust and compact single-unit solution. Vertically stacking the Y-Fi HP pump laser and OPA eliminates the need for beam routing on the table, which creates an optical system that is less sensitive to environmental changes. Since the Y-Fi HP fiber laser functions as the base unit of the vertical stack, the compact 464 mm x 304 mm footprint is retained, saving valuable work space on the optical table.

The front panel of the Y-Fi OPA features output ports for the signal, depleted pump, and idler beams, as well as a multimode SMA connector that can be connected to a spectrometer for signal monitoring (see the callouts on the schematic in the Specs tab). Each output has a beam height of 5". As a result of its vertical stacking architecture, the Y-Fi OPA also provides full access to the Y-Fi HP pump beam via a bypass port; please see the full Y-Fi Ultrafast Ytterbium Fiber Laser web presentation for detailed specifications.

For hands-free operation and long-term reliability, the Y-Fi OPA features a user-friendly GUI that controls parameters such as wavelength, repetition rate, time overlap offset, and pulse compression offset. The included software allows the user to easily switch between the Y-Fi OPA and Y-Fi HP modes of operation; please note that there will not be output from the signal, idler, or depleted pump while in Y-Fi HP mode.

Applications to Three-Photon Microscopy
With a high peak power, tunable repetition rate, and wide wavelength tunability, the Y-Fi OPA is optimized for three-photon microscopy, which requires efficient fluorescence excitation to achieve deep imaging depths. The featured NIR and MIR tunable wavelength range is appropriate for exciting the fluorescent proteins GFP and RFP, which have excitation wavelengths of 1300 nm and 1700 nm, respectively. By including a tunable repetition rate, the user has the flexibility to adjust the imaging frame rate to accommodate the time scales of various processes or events, as well as control the average power incident on a sample to reduce heat-induced degradation.

Thorlabs has recently acquired the Y-Fi™ Family of Ultrafast Ytterbium Fiber Lasers from KMLabs and is currently finalizing the compliance requirements for international sale of these items. The information presented in this web presentation and the attached datasheet reflect current specifications for these items. Additional details, including potential updates to the specifications, will be provided once an internal evaluation of the product line is completed. In the interim, please contact LaserSales@thorlabs.com to learn more about our Y-Fi™ products.

Laser Specifications
Output Beam	Signal	Idler	Pump
Output Wavelength	1275 - 1800 nm	2.4 - 4.4 μm	1035 nm
Repetition Rate (Tunable)	1 - 4 MHz		1 - 10 MHz
Output Power (Average)^a	>1.5 W @ 4 MHz	>0.25 W @ 4 MHz	>20 W @ 10 MHz
Pulse Energy^a	>0.4 μJ @ 1 MHz	>0.1 μJ @ 1 MHz	>3 μJ at 1MHz
Beam Quality	M²< 1.4	-	M² < 1.2
Polarization	S-Polarized (Vertical); Linear
Power Stability @ 1330 nm	<2% RMS over 12 hrs	-	-
Support Documentation
Datasheet

These specifications are given for the peak of the tuning curve.

Click to Enlarge
The Y-Fi™ OPA features four output ports, which are for the Y-Fi™ HP pump, signal, depleted pump, and idler beams. A multimode SMA connector is also included for signal monitoring.

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Y-Fi OPA Pulse Energy and Average Power Scaling with Repetition Rate Measured at 1330 nm

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Y-Fi OPA Pulse Energy and Average Power Scaling with Repetition Rate Measured at 1680 nm

Pulsed Laser Emission: Power and Energy Calculations

Click above to download the full report.

Determining whether emission from a pulsed laser is compatible with a device or application can require referencing parameters that are not supplied by the laser's manufacturer. When this is the case, the necessary parameters can typically be calculated from the available information. Calculating peak pulse power, average power, pulse energy, and related parameters can be necessary to achieve desired outcomes including:

Protecting biological samples from harm.
Measuring the pulsed laser emission without damaging photodetectors and other sensors.
Exciting fluorescence and non-linear effects in materials.

Pulsed laser radiation parameters are illustrated in Figure 1 and described in the table. For quick reference, a list of equations are provided below. The document available for download provides this information, as well as an introduction to pulsed laser emission, an overview of relationships among the different parameters, and guidance for applying the calculations.

Equations:
Period and repetition rate are reciprocal:		and
Pulse energy calculated from average power:
Average power calculated from pulse energy:
Peak pulse power estimated from pulse energy:
Peak power and average power calculated from each other:
	and
Peak power calculated from average power and duty cycle*:
	*Duty cycle () is the fraction of time during which there is laser pulse emission.

Click to Enlarge

Figure 1: Parameters used to describe pulsed laser emission are indicated in the plot (above) and described in the table (below). Pulse energy (E) is the shaded area under the pulse curve. Pulse energy is, equivalently, the area of the diagonally hashed region.

Parameter	Symbol	Units
Pulse Energy	E	Joules [J]	A measure of one pulse's total emission, which is the only light emitted by the laser over the entire period. The pulse energy equals the shaded area, which is equivalent to the area covered by diagonal hash marks.
Period	Δt	Seconds [s]	The amount of time between the start of one pulse and the start of the next.
Average Power	P_avg	Watts [W]	The height on the optical power axis, if the energy emitted by the pulse were uniformly spread over the entire period.
Instantaneous Power	P	Watts [W]	The optical power at a single, specific point in time.
Peak Power	P_peak	Watts [W]	The maximum instantaneous optical power output by the laser.
Pulse Width		Seconds [s]	A measure of the time between the beginning and end of the pulse, typically based on the full width half maximum (FWHM) of the pulse shape. Also called pulse duration.
Repetition Rate	f_rep	Hertz [Hz]	The frequency with which pulses are emitted. Equal to the reciprocal of the period.

Example Calculation:

Is it safe to use a detector with a specified maximum peak optical input power of 75 mW to measure the following pulsed laser emission?

Average Power: 1 mW
Repetition Rate: 85 MHz
Pulse Width: 10 fs

The energy per pulse:

seems low, but the peak pulse power is:

It is not safe to use the detector to measure this pulsed laser emission, since the peak power of the pulses is >5 orders of magnitude higher than the detector's maximum peak optical input power.

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Femtosecond Optical Parametric Amplifier (OPA)

Features

Applications

Pulsed Laser Emission: Power and Energy Calculations