High Extinction Filters for SPDC Applications

Filters for Spontaneous Parametric Down Conversion (SPDC) Applications
OD_abs ≥ 10 Blocking of Pump Photons, >99% Transmission of SPDC Photons
Greater Blocking Without Loss of Transmission From Multiple Stacked Filters
Ø12.5 mm and Ø25.0 mm Mounted Filters

Transmission Direction Indicator

FBHQ810

Ø25.0 mm High Extinction Filter, 405 nm Pump Rejector, 810 nm Signal/Idler

FBHQ1550

Ø25.0 mm High Extinction Filter, 775 nm Pump Rejector, 1550 nm Signal/Idler

FBHQ51550

Ø12.5 mm High Extinction Filter, 775 nm Pump Rejector, 1550 nm Signal/Idler

Application Idea

Single Photon Counting Setup Using an FBHQ810 Filter Mounted to a SPDMH3 Detector after the NLCQ6 β-BBO Crystal (Mounts and Assemblies Sold Separately)

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Overview
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General Specifications
Item #	FBHQ810, FBHQ5810	FBHQ1550, FBHQ51550
Optical Density	OD_abs ≥ 10 at 405 nm	OD_abs ≥ 10 at 775 nm
Transmission	>99.0% at 810 nm	≥99.5% at 1550 nm
Substrate	AF32	Silicon
Unmounted Thickness	0.5 mm	0.68 mm
Mounted Thickness	3.5 mm
Housing Diameter	12.5 mm or 25.0 mm
Clear Aperture	Ø10 mm for Ø12.5 mm Ø21.1 mm for Ø25.0 mm
Surface Quality	60-40 Scratch-Dig
Coating	AR Coated (Front and Back Surfaces)
Parallelism	<3 arcmin
Housing	Mounted in Black Anodized Aluminum Ring
Edge Markings	Item #, Engraved Arrow^a

The engraved arrow indicates the recommended direction of light transmission. The performance of the filter is consistent for either forward and backward propagating light.

Packaging Redesign

Thorlabs is investing in green initiatives to replace plastic and foam optics packaging with more sustainable solutions. Leave feedback or learn more about what went into the design of our pilot program for Ø1" single optics here.

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Our new case is made from recyclable steel and includes recyclable paper inserts to protect the optic inside

Features

Ultra-High Blocking of OD_abs ≥ 10 at 405 nm and 775 nm Pump Wavelengths
Transmission >99.0% at 810 nm and >99.5% at 1550 nm Signal/Idler Wavelengths
Designed for Single Photon Counting and SPDC Applications

Thorlabs offers hard-coated high extinction filters that are designed to be used as filters for Type-0, Type-I, or Type-II SPDC, a nonlinear process where a single high-energy pump photon is down converted into a signal and idler pair of lower-energy photons, conserving both energy and momentum in the process. See our β-BBO or PPKTP Crystals specially designed for SPDC for more detailed information.

Our high extinction filters allow for distinguishing between pump and signal/idler photons by suppressing pump photons (OD_abs ≥ 10) while providing >99% transmission at the signal/idler wavelengths with an anti-reflective (AR) coating to minimize reflective losses. This reduces the need to stack multiple filters to achieve the necessary OD to block the pump wavelength while offering a greater transmission of signal/idler light. For more transmission information, see the icons below.

The FBHQ1550 and FBHQ51550 filters are designed to block a 775 nm pump using an AR coated silicon substrate that absorbs the 775 nm photons while being transparent to the 1550 nm signal and idler photons. The FBHQ810 and FBHQ5810 filters use a coating designed to absorb 405 nm photons on an AF32 substrate to block 405 nm pump photons while transmitting 810 nm signal and idler photons.

Each filter is mounted in a Ø12.5 mm or Ø25.0 mm black anodized aluminum housing that is labeled with an arrow indicating the design propagation direction. The housing makes handling easier and limits scattering of light. These filters can be mounted in our extensive line of filter mounts and wheels. As the mounts are not threaded, retaining rings will be required to mount the filters in one of our internally threaded lens tubes. We do not recommend removing the filter from its mount as the risk of damaging the filter is very high.

Optics for Spontaneous Parametric Down Conversion (SPDC)
β-BBO Crystals for SPDC	PPKTP Crystals for SPDC	High Extinction Filters

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High Extinction Filters, 810 nm Signal/Idler, 405 nm Pump Rejector

Item #^a	Transmission	Optical Density	Transmission Data^b	TWE^c	Surface Quality	Mounted Thickness	Clear Aperture	Outer Diameter
FBHQ5810	810 nm (T > 99.0%)	OD_abs ≥ 10 @ 405 nm		λ/4 at 1064 nm	60-40 Scratch-Dig	3.5 mm	Ø10 mm	Ø12.5 mm
FBHQ810	810 nm (T > 99.0%)	OD_abs ≥ 10 @ 405 nm		λ/4 at 1064 nm			Ø21.1 mm	Ø25.0 mm

All specifications are valid for an AOI up to 10°.
Click on for a plot and downloadable data. Please note that transmission is only guaranteed for the specified wavelength and that the data in the plots is typical. Performance may vary from lot to lot.
Transmitted wavefront error (RMS) over the clear aperture.

High Extinction Filters, 1550 nm Signal/Idler, 775 nm Pump Rejector

Item #^a	Transmission	Optical Density	Transmission Data^b	TWE^c	Surface Quality	Mounted Thickness	Clear Aperture	Outer Diameter
FBHQ51550	1550 nm (T > 99.5%)	OD_abs ≥ 10 @ 775 nm		λ/4 at 1064 nm	60-40 Scratch-Dig	3.5 mm	Ø10 mm	Ø12.5 mm
FBHQ1550	1550 nm (T > 99.5%)	OD_abs ≥ 10 @ 775 nm		λ/4 at 1064 nm			Ø21.1 mm	Ø25.0 mm

All specifications are valid an AOI up to 10°.
Click on for a plot and downloadable data. Please note that transmission is only guaranteed for the specified wavelength and that the data in the plots is typical. Performance may vary from lot to lot.
Transmitted wavefront error (RMS) over the clear aperture.