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Dichroic Atomic Vapor Spectroscopy Kit

  • Ideal for Laser Locking or Teaching Labs
  • Rubidium or Potassium Vapor Cells Available Separately


See the DAV Spectroscopy Tab Below
for Measurement Details


Rubidium Vapor Cell

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Spectroscopy Systems Selection Guide
Dichroic Atomic Vapor Spectroscopy (DAVS) Systems
Saturated Absorption Spectroscopy (SAS) Systems
Long-Term Stability <2 MHz (RMS)
Required Input Power ~100 µW
Input Fiber Termination* FC/PC
Wide Capture Range ~500 MHz
Detector Bandwidth 1 MHz
Detector Output Range ±10 V
Reference Cell Temperature 50 °C (Max)

*Alternate fiber inputs are available. Please contact


  • Dichroic Atomic Vapor Spectroscopy (DAVS) for Locking to Transitions
  • Rubidium, Potassium, and Custom Vapor Cells Available
  • PM Fiber-Coupled Setup
  • Ideal for Locking Tunable Lasers or Teaching Labs

The Thorlabs SKDAV kit consists of a proven set of components to construct a compact, fiber-coupled dichroic atomic vapor spectroscopy (DAVS) setup. It offers a method for producing a highly stable lock for tunable lasers, with a wide capture range, low power requirements, and steep signal slope. The kit also allows for the study of the Zeeman effect in atomic transitions.

The kit has been designed using stock optics and mechanics as well as compatible custom components, making it compatible with other Thorlabs cage system and lens tube components. For a list of the major components and subsystems included in the DAVS kit, please see the Kit Contents tab.

While the vapor cell heater is included in the kit, please note that the vapor cell and temperature controller must be purchased separately. Currently, we offer rubidium and potassium reference vapor cells, which are available below. A variety of custom vapor cells are also available; please contact for more details. Thorlabs' TC200 Temperature Controller is compatible with the cell heater and sold seporately below.

Dichroic Atomic Vapor Spectroscopy
Dichroic Atomic Vapor Spectroscopy (DAVS) utilizes the Zeeman effect to create a signal suitable for laser locking. A rubidium vapor cell is placed in a weak longitudinal magnetic field. The Zeeman splitting of the atomic transitions allows for wavelength locking at locations off of resonance peaks. For a detailed tutorial on DAVS, please see the DAV Spectroscopy tab.

Custom Options and Assembly Services
Our spectroscopy kits are adaptable to most tunable lasers with user-supplied feedback mechanisms. While our standard kit is designed to accept PM fiber-coupled sources, we can also offer kits for free-space input. We can also offer assembly services upon request. To discuss these and other custom options, please contact us at

Please note that the Spectroscopy Kits do not come with vapor cells or a temperature controller. Rubidium and Potassium vapor cells are available below. Thorlabs offers the TC200 temperature controller that is compatible with the gas cell heater provided with the kit below.

DAVS Kit Contents

Thorlabs' DAVS Kit contains the following subsystems:

Fiber Input and Polarizer

The fiber input is designed with our F220FC-780 fiber collimator and cage system components. The F220FC-780 collimates the input from an FC/PC-terminated PM fiber, which must be purchased separately. For Rubidium, we recommend using our P1-780PM-FC-5 patch cable. For users who would prefer a free-space input, please contact us at for a quote for a kit without the fiber collimator and mounting mechanics.

Once the light is collimated, the beam passes through a calcite Glan-Laser polarizer to ensure polarization purity. Both the fiber collimator and polarizer are provided with our cage system mounts, which easily allows for the user to add other components using our 30 mm cage system.

Vapor Cell Heater and Magnets

This assembly consists of our GCH25-75 vapor cell heater and a permanent magnet assembly specifically designed for the DAVS kit. Both magnets feature a hole in the center to allow the light to pass, and they attach to the gas cell heater using cage system ER rods included with the heater. The magnets are easily removed so that both absorption and DAV spectra may be measured.

Please note that neither vapor cells nor a temperature controller for the GCH25-75 are included with the SKDAV. Rubidium and Potassium cells are available on the bottom of this page, and other atomic vapor cells are available upon request. Thorlabs offers the TC200 temperature controller which is compatible with the vapor cell heater.

Output Prism

After exiting the vapor cell and magnet assembly, the light will consist of two counter-rotating circular polarizations, which will be absorbed at either red- or blue-shifted frequencies (see the DAV Spectroscopy Tab for details). A zero-order quarter-wave plate (WPQ05M-780) will map the circular polarizations onto orthogonal linear polarizations. These linear polarizations are then split by a Wollaston Prism (WP10-B) at an angle of 20°.

Both polarization optics are mounted into 30 mm cage system rotation mounts (the quarter-wave plate is mounted into a CRM1P while the prism is mounted using a CRM1. The CRM1P features a micrometer that allows for very small adjustments of the wave plate, which in turn leads to finer adjustments of the locking frequency. The use of these cage system and SM1 lens tube mounts would allow easy addition of additional optics or mechanical components according to experimental needs.

Schematic of Beam Path

Mirrors and Balanced Detector

A square folding mirror and kinematic mirror mount are included to direct the output of the Wollaston prism so that the assembly can be made more compact. If space is not an issue, this mirror can be left out of the system. After reflecting off of the square mirror, the two orthogonal polarizations are reflected separately by Ø1/2" mirrors, so that the beams can be aligned with the two inputs of our PDB210A balanced detector. The image to the right shows the beam path through the entire system, which illustrates the function of the mirrors. The balanced detector allows for measurement of three output voltages: the separate signals recorded from each photodiode, as well as the difference between the two measurement channels. This difference channel provides the DAVS signal, which can be used for a stable laser lock. The other two chanels are useful for alignment of the system, as well as to illustrate the principles of DAVS in teaching labs.

Dichroic Atomic Vapor Spectroscopy

DAVS Illustration
Figure 1. In the absence of a magnetic field, the absorption profile is independent of polarization, as shown by the red line in the graph. After a longitudinal magnetic field is applied, the Zeeman shift can be observed for the two circularly polarized components (green and blue lines). The useful DAVS signal is the difference between the absorption profiles of these two components.

Dichroic Atomic Vapor Spectroscopy utilizes the Zeeman effect to create a stable frequency lock for a laser. A vapor cell is placed in a weak longitudinal magnetic field, and linear polarized light passes through the cell. Due to the presence of the weak magnetic field, the absorbtion profiles of the two circularly polarized components (left and right) that comprise the linearly polarized input beam are shifted to higher and lower frequencies, respectively. After passing through the vapor cell, the beam propagates through a quarter-wave plate and a polarizing beamsplitter. A dispersion-like curve is generated, which provides an error signal for the frequency lock.

The following tutorial gives details on the basics of how DAVS spectroscopy works and how it can be utilized to lock a single-frequency laser, and the advantages of our DAVS system.

Zeeman Splitting due to a Magnetic Field
In the presence of a magnetic field, the hyperfine transitions will be split by the Zeeman effect. In the absence of a magnetic field, the absorption of an atomic vapor is independent of the polarization of the excitation source. This is shown by the red line in Figure 1. If the light is linearly polarized, it can be thought of as a superposition of counter-rotating circular polarizations (left and right).

The DAVS System
The DAVS system consists of an atomic vapor cell in a weak longitudinal magnetic field. The schematic of the system is shown in Figure 2. The input laser light travels through a Glan-Taylor polarizer prior to entering the vapor cell, ensuring that the light is linearly polarized. After propagating through the vapor cell, the beam passes through a quarter-wave plate and a Wollaston prism, which serves as a polarizing beamsplitter.

DAVS System Schematic
Figure 2. Schematic of the DAVS system.

DAVS Rb Signal
Figure 3. Using DAVS, a laser can be locked to any of the zero crossings in the above signal. The circled zero crossings correspond to transitions in atomic Rb, each of which can be tuned by approximately 500 MHz.

Due to the presence of the magnetic field, the absorption profiles will be split as shown in Figure 1; the initial linear polarizer ensures that the light will be in one of the two circular polarization states to interact with the two Zeeman-split absorbtion curves. The quarter-wave plate will map the two circular polarization components into two orthogonal linear polarization components, which are then split by the Wollaston prism to be detected by the balanced detector. The resulting measured signal is the difference between the two Zeman-split absorption curves, and is the yellow line shown in Figure 1.

One of the advantages of the DAVS system lies in the quarter-wave plate. If the waveplate's axes are 45° from the axis of the input Glan-Taylor polarizer, then the two absorption components will be equal in intensity after being split by the Wollaston prism. The laser is locked to the zero-crossing in the signal measured by the balanced detector. The zero crossings for the Rb D2 transition are shown in Figure 3. As the quarter-wave plate is rotated, the two absorption profiles will pass through with differing intensities; this will cause the zero-crossing point to shift; in Thorlabs' DAVS kit, each of the locking points can be tuned by up to 500 MHz, which is referred to as the capture range.

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Dichroic Atomic Vapor Spectroscopy Kit

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Imperial Price Available / Ships
SKDAV Support Documentation
SKDAVDichroic Atomic Vapor Spectroscopy Kit
Lead Time
+1 Qty Docs Part Number - Metric Price Available / Ships
SKDAV/M Support Documentation
SKDAV/MDichroic Atomic Vapor Spectroscopy Kit, Metric
3-5 Days

Spectroscopy Kit-Compatible Vapor Cells

Thorlabs offers Potassium and Rubidium cells that are compatible with our Spectroscopy Kits. These reference cells are fabricated from Pyrex, a rugged material known to resist chipping and cracking, and incorporate flat windows made from optical-quality Schott Borofloat glass. They are tested to ensure that the transmission through the cell exceeds 84% for light in the 350 nm to 2.4 µm range. The content of each reference cell is also tested by measuring the absorption spectrum of a well known transition using a tunable diode laser.

Please note: These reference cells are subject to hazardous goods regulations and must be shipped separately using specifically regulated shipping methods and may require special shipping and handling charges. Next day delivery is not available. All orders will ship from our US warehouse regardless of destination and cannot be returned. Due to hazardous materials shipping regulations, we are currently unable to ship our reference cells to Brazil, China, or Uruguay.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
GC25075-K Support Documentation
GC25075-KPotassium Borosilicate Reference Cell, Ø25 mm x 71.8 mm
GC25075-RB Support Documentation
GC25075-RBRubidium Borosilicate Reference Cell, Ø25 mm x 71.8 mm

* Vapor Cell Purchases are not eligible for return.

Heater Controller

  • Heating from 20 °C to 200 °C
  • User-Selectable Display Units (°F, °C, or K)
  • Run Standalone or via Software
  • Adjustable PID
  • Compatible with Positive and Negative Temperature Coefficient Thermistors

The TC200 Heater Controller is a benchtop controller intended for use with resistive heating elements rated up to 18 W, including the heaters in the Temperature-Controlled Liquid Crystal Retarders sold on this page. The unit will display the temperature in either °F, °C, or K, and can be programmed for up to five sequential temperature settings along with associated ramp and hold times for each level. A user programmable maximum temperature limit provides protection to the device being heated and a user-programmable power limit protects the heating element from being over driven. Other safety features include an Open Sensor Alarm that will shut down the driver if the temperature sensing element is missing or becomes disconnected.

Capable of stand-alone operation from a simple keypad interface, the TC200 can be interfaced with a PC using a standard USB Type B connector using our TC200 Application Program, LabVIEW drivers, LabWindows drivers, or using a simple command-line interface from any terminal window.

The TC200 is shipped with a 120 VAC power cord for use in the US while the TC200-EC is shipped with a 230 VAC power cord for use in Europe. If you require a power cord for another country, please contact your local sales office.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Imperial Price Available / Ships
TC200 Support Documentation
TC200Temperature Controller, 120 VAC Power Cord
+1 Qty Docs Part Number - Metric Price Available / Ships
TC200-EC Support Documentation
TC200-ECTemperature Controller, 230 VAC Power Cord

12 VDC Regulated Power Supply

  • Replacement Power Supply for the Dichroic Atomic Vapor Spectroscopy System Sold Above
  • ±12 VDC Power Output
  • Current Limit Enabling Short Circuit and Overload Protection
  • On/Off Switch with LED Indicator
  • Switchable AC Input Voltage (115 or 230 VAC)
  • Replacement Power Supply for the Dichroic Atomic Vapor Spectroscopy System Sold Above
  • 6.6 ft (2 m) Cable with LUMBERG RSMV3-657/2M Male Connector
  • UL and CE Compliant

The LDS1212 ±12 VDC Regulated Linear Power Supply is intended as a replacement for the supply included with our dichroic atomic vapor spectroscopy systems sold on this page. The cord has three pins: one for ground, one for +12 V, and one for -12 V (see diagram above). This power supply ships with a location-specific power cord and the voltage switch is set to the proper setting for your location before it is shipped. This power supply can also be used with our PDA series of amplified photodetectors, our PDB series of balanced photodetectors, our PMM series of photomultiplier modules, and our APD series of avalanche photodetectors.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
LDS1212 Support Documentation
LDS1212±12 VDC Regulated Linear Power Supply, 6 W, 115/230 VAC
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