Features

Components Compatible with Thorlabs' Tunable Laser Kits
Convert Laser Between Littman and Littrow Configurations
Alter Cavity to Support Other Gain Chips

This page includes products that are direct replacements of standard components in the Tunable Laser Kit and can be used to customize a tunable laser kit's performance. By using these components, customers can replace standard components, switch between cavity configurations, and alter the laser's performance. The images and tables immediately below label the components in our standard Tunable Laser Kits.

Littman Tunable Laser Kits

Label	Description	Label	Description
A	Tuning Motor Mount	F	Collimating Lens
B	Gain Chip Mounting Plate	G	Littman Grating Platform
C	Half Butterfly Gain Chip	H	Littman Grating Module
D	Collimation Adjuster	I	Littman Mirror Module
E	Mode Hop Adjuster	J	Tuning Motor

Littrow Tunable Laser Kits

Label	Description	Label	Description
A	Tuning Motor Mount	E	Mode Hop Adjuster
B	Gain Chip Mounting Plate	F	Collimating Lens
C	Half Butterfly Gain Chip	G	Littrow Grating Module
D	Collimation Adjuster	H	Tuning Motor

Click to Enlarge

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This link opens a document that contains a comprehensive list of performance specifications and performance plots.

All quoted values are typical. Please see the gain chip's Spec Sheet (linked below) for the most detailed information on performance.

General Specifications
Item #	Spec Sheet	Reference Cavity	CWL^a	Tuning Range^{a, b}	Peak Power^a	Chip Gain^c	Gain Ripple	R₁	R₂	Chip Length
TFP780A		TLK-L780M	770 nm	30 nm	50 mW	-	3 dB	0.01%	90%^d	0.75 mm
SAF1171S		TLK-L1050M	1050 nm	60 nm	8 mW	30 dB	2.5 dB (Max)	0.005%	10%^e	1 mm
SAF1175S		Littmann Cavity (Offered as OEM)	1220 nm	90 nm	40 mW	17 dB	0.5 dB	0.005%	10%^e	1 mm
SAF1174S		TLK-L1300R	1310 nm	100 nm	50 mW	35 dB	0.35 dB	0.005%	10%^e	2 mm
SAF1550S2		TLK-L1550R	1550 nm	120 nm	40 mW	17 dB	0.4 dB (Max)	0.005%	10%^e	1 mm
SAF1550P2		TLK-L1550R	1550 nm	120 nm	40 mW	17 dB	0.4 dB (Max)	0.005%	10%^e	1 mm
SAF1900S		TLK-L1900M	1900 nm	120 nm	7 mW	18 dB	1.5 dB	0.005%	20%^e	2 mm

All values are typical, unless otherwise indicated.
^a The values given in the highlighted columns were measured in the specified reference cavity. Different external cavities will produce different performance specifications.
^b 10 dB point.
^c Single-pass optical gain at center of gain curve.
^d Refer to the FP chip reflectivity diagram below.
^e Refer to the SAF chip reflectivity diagram below.

ASE Specifications
Item #	Center Wavelength (Typ.)	3 dB Bandwidth (Typ.)	ASE Current	Operating Current (Typ.)	Operating Current (Max)
TFP780A	780 nm	30 nm	80 mA (Typ.)	140 mA	180 mA
SAF1171S	1050 nm	60 nm	150 mA (Max)	-	150 mA
SAF1175S	1220 nm	80 nm	200 mA (Typ.)	200 mA	-
SAF1174S	1320 nm	80 nm	600 mA (Typ.)	500 mA	800 mA
SAF1550S2	1550 nm	80 nm	300 mA (Typ.)	300 mA	500 mA
SAF1550P2	1550 nm	80 nm	300 mA (Typ.)	300 mA	500 mA
SAF1900S	1930 nm	150 nm	400 mA (Typ.)	500 mA	800 mA

Note: The light polarization is vertical inside the Fabry-Perot Gain Chip, while the light polarization is horizontal inside the SAF Gain Chips.

SAF Reflectivity Drawing

*R₂ = 10% for all models in the SAF series except the SAF1900S, for which R₂ = 20%.

FP Reflectivity Drawing

Fabry-Perot Gain Chip Lasing Performance Using Littman Tunable Laser Kit

The Fabry-Perot (FP) laser diode has the two parallel ends of the semiconductor cleaved atomically flat to produce an oscillating cavity. Laser light is typically emitted through one of these highly reflective edges, using the semiconductor as the gain medium. FP lasers typically lase in a single longitudinal mode and exhibit temperature-dependent tunability over a small range. Since the end facets of the chip form the laser cavity, different longitudinal modes also appear in the emission, broadening the linewidth (100 - 1000 GHz). Given below are the typical TFP780A spectra and details on the packaged devices.

Part #	Center Wavelength	Power vs. Current	Power Spectrum
TFP780A	770 nm

Basic Littman Configuration

Fabry-Perot Gain Chip Drawing

Fabry-Perot Gain Chip

SAF Gain Chip Lasing Performance Using Littrow Tunable Laser Kit

The innovative design of an SAF gain chip is ideal for use in external cavity lasers because it virtually eliminates unwanted feedback from the intracavity facet of the gain chip. These devices offer superior performance in a wide variety of external cavity configurations. Given below are typical spectra and details on the packaged devices.

Part #	Center Wavelength	Power vs. Current	Power Spectrum
SAF1171S	1050 nm
SAF1175S	1220 nm
SAF1174S*	1320 nm
SAF1550S2	1550 nm
SAF1550P2	1550 nm
SAF1900S	1900 nm

*Please note that the fluctuations in the power spectrum between 1350 and 1380 nm are associated with water vapor absorption. The power at these wavelengths can be improved by purchasing the TLK-E sealed laser enclosure and purging the enclosure with gas.

Basic Littrow Configuration

Fiber-Coupled SAF Gain Chip Drawing

SAF Gain Chip

Littrow Schematic
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Littman Schematic
Click to Enlarge

Cavity Design	Littrow	Littman-Metcalf
High Output Power	x
Wide Tuning Range	x
Narrow Linewidth		x
Stationary 0^th Order Beam		x

Lasers consist of an active gain element and optical feedback to this gain element. The most common diode lasers are based on a Fabry-Perot design with a linear waveguide and reflective surfaces at both ends of the gain chip to provide feedback. Some Fabry-Perot lasers are constructed for external feedback, but this is rare. Single angle facet (SAF) gain chips, on the other hand, have a curved waveguide with only one internally reflective endface and rely on external optical feedback to produce lasing.

Through the use of an external feedback mechanism, a user is able to tune a laser cavity to sustain a desired wavelength with minimal linewidth. This is highly desirable for many applications, particularly in metrology where precision is essential. Littrow and Littman-Metcalf configurations are the two most common ways to build an External Cavity Laser (ECL). Many other ECL configurations are based on these designs, but typically modify the cavity with additional optical components. Littrow cavities have minimal losses and thus intrinsically offer higher power, while Littman-Metcalf cavities produce a narrower linewidth.

A Littrow cavity provides feedback to the gain element through the use of a grating. One end of the gain element must allow light to exit, such as the design of an SAF. Light emitted from this end is first collimated. A grating then diffracts this collimated beam with the 1^st order diffraction coupled back into the gain element, which allows it to support lasing. Wavelength tuning of the laser is possible by altering the angle of the grating relative to the cavity. 0^th order diffraction from the grating will exit the laser's cavity at an angle dependent on the grating angle.

Littman-Metcalf configured ECLs use both a grating and a mirror for tuning. Similar to the Littrow configuration, light emitted from the uncoated end of the gain element must first be collimated. This beam is then diffracted by a grating. The 0^th order diffraction reflects off of a mirror back on to the grating, where it is diffracted a second time before being coupled back into the gain element. Since light is diffracted twice, losses are higher (power loss), but the side mode suppression ratio (SMSR) is increased to produce a narrower linewidth laser. In this configuration the grating remains stationary, while the mirror is turned to tune the laser cavity's supported wavelength. Unlike with Littrow lasers, the direction of the 0^th order free space beam remains stationary, which can be beneficial in some applications.

Many modifications to these cavities can be made to produce a higher polarization extinction ratio (PER) or to improve the SMSR. We always seek to tailor our products to our customers' applications. Please contact Tech Support and let us know what accessories would benefit your application.

Littman Cavity Configurations

These are the differentiating components of each Littman Tunable Laser Kit. The Gain Chip, Top Plate, Grating Module, and Collimating Lens are the components you will need to convert from one supported wavelength to the next. If you are converting your Littrow Tunable Laser Kit to a Littman configuration, you will also need to purchase a Littman Mirror Module (TLK-LMM) and a Littman Grating Platform (TLK-LGP).

Included in Kit Item #	Center Wavelength	Gain Chip	Top Plate	Grating Module	Collimating Lens
TLK-L780M	770 nm	TFP780A	TLK-P00	TLK-G1500M	TLK-352330-B
TLK-L1050M	1050 nm	SAF1171S	TLK-P26	TLK-G1150M	TLK-352230-B*
TLK-L1300M	1310 nm	SAF1174S	TLK-P26	TLK-G0900M	TLK-352330-C
TLK-L1550M	1550 nm	SAF1550S2	TLK-P26	TLK-G0750M	TLK-352330-C
TLK-L1550M	1550 nm	SAF1550P2	TLK-P26	TLK-G0750M	TLK-352330-C
TLK-L1900M	1900 nm	SAF1900S	TLK-P26	TLK-G0600M	TLK-352230-C*

*Coming Soon

Littrow Cavity Configurations

These are the differentiating components of each Littrow Tunable Laser Kit. The Gain Chip, Top Plate, Grating Module, and Collimating Lens are the components you will need to convert from one supported wavelength to the next. If you are converting from a Littman to a Littrow configuration, you will not need any additional components than the ones listed below.

Included in Kit Item #	Center Wavelength	Gain Chip	Top Plate	Grating Module	Collimating Lens
TLK-L1220R	1220 nm	SAF1175S	TLK-P26	TLK-G1350R2	TLK-352230-C*
TLK-L1300R	1310 nm	SAF1174S	TLK-P26	TLK-G1350R	TLK-352230-C*
TLK-L1550R	1550 nm	SAF1550S2	TLK-P26	TLK-G1050R	TLK-352230-C*
TLK-L1550R	1550 nm	SAF1550P2	TLK-P26	TLK-G1050R	TLK-352230-C*
TLK-L1950R	1950 nm	SAF1900S	TLK-P26	TLK-G0900R	TLK-352230-C*