Universal and compact laser stabilization electronics

LaseLock is a universal and compact laser frequency stabilization electronics (“lock-box”), which can be used to frequency stabilize lasers (such as diode lasers, Ti:sapphire or dye lasers).

Stabilized lasers are sought-after components for many applications. By using LaseLock, laser drift can be almost completely eliminated and very narrow line widths can be generated with extreme stability. LaseLock measures and detects frequency changes of the laser and provides corresponding feedback signals so that these changes can be corrected and stabilized.

In particular, optical resonators or atomic absorption or fluorescence lines serve as frequency references. These reference components are also available from TEM Messtechnik:

  • CoSy → offers reference standards based on saturation spectroscopy, with cesium, rubidium or potassium cells available
  • iScan → is an active Fabry Perot interferometer, which can provide a stabilization signal at any frequency (“active frequency correction”)

Conversely, it is possible to control optical resonators to a given laser frequency using mechanical actuators. The drivers required for this are optionally available for LaseLock (HV-driver for piezo actuators, HC-driver for galvos or DLD-driver for diode lasers, incl. temperature and current control).

Key Features

  • Compact, autonomous lock-in electronics for diode lasers, dye lasers, Ti:Sa lasers or optical resonators
  • Built-in dither generator
  • Side-of-fringe and top-of-fringe stabilization
  • at least 2 independent PID controllers
  • Lock-in point validity detection and automatic “search” function
  • Built-in oscilloscope functionality
  • User interface with touch screen and color signal display
TFT Screen Laser Stabilization LaseLock - Scan function
TFT Screen Laser Stabilization LaseLock - Scan function

LaseLock® scans the laser frequency. Users can search the absorption lines and select the desired line peak for regulation using two threshold values (red and blue line).

TFT Screen Laser Stabilization LaseLock - dither generator
TFT Screen Laser Stabilization LaseLock - dither generator

The built-in dither generator modulates the output voltage. The demodulated input signal is used for regulation. The yellow line defines the set point level.

TFT Screen Laser Stabilization LaseLock - lock-mode
TFT Screen Laser Stabilization LaseLock - lock-mode

In “lock-mode”, LaseLock stabilizes the frequency to a desired absorption peak. Input signal and user-defined thresholds are constantly compared  – the controller searchs and relocks automatically as soon as the signal exceeds the thresholds.

Application example

Stabilization of the frequency of a diode laser with external resonator to an atomic absorption line

In this application, the frequency of a tunable laser is stabilized with the help of a reference cell. Suitable lasers can be tunable diode lasers, Ti:Sa or dye lasers, for example.

The aim is to set the laser frequency to a value at which the sample has maximum absorption (or minimum absorption).

This application requires the following components:

  • 1x digital LaseLock with HV option
  • 1x laser with tuneable frequency, here via piezo-actuator (e.g. TOPTICA DL100 diode laser)
  • 1x spectroscopic absorption cell*
  • 1x beam splitter
  • 2x photo detectors

*  We recommend to use the compact spectroscopy module CoSy →, which includes a complete setup for Doppler-free saturation absorption spectroscopy.

Principle of Operation

Two different methods can be applied:

  • Side-of-fringe stabilization
  • Top-of-fringe stabilization (to maximum or minimum, ‘lock-in’-technique)

Side-of-fringe stabilization is used when a direct discriminator signal can be derived from the measurement signal. In other words, the slope of the peak signal is used to convert frequency fluctuations of the laser into amplitude fluctuations, which can be detected and subsequentely stabilized.

Flankenstabilisierung (side-of-fringe stabilization)

Side-of-fringe stabilization

Top-of-fringe stabilization uses a modulation technique and phase-synchronous detection.

For this, the laser frequency (or a different physical measure like the resonator length) is modulated, a detector signal is multiplied with the modulation signal, and then the product signal is averaged by a low pass filter. The resulting ‘lock-in’-signal represents the derivative of the signal with respect to the laser frequency (or the respective varied physical measure).

This signal can be used directly for physical examinations, because in most cases it contains less disturbing signal parts (noise, offsets) than the directly measured signal.

The zero-crossing of the derivative represents a maximum (or minimum) of the detected signal structure. For stabilization of a laser or resonator towards such an extremum, the ‘lock-in’ signal is processed by a regulator, which generates a suitable control signal that is fed back (either directly, or for piezo actuators via a high-voltage amplifier) to the frequency-determining element of the laser (or resonator). In this way the control loop is closed and the laser (or resonator) is locked actively to the maximum (or minimum).

Maximum- (Minimum-) Stabilisierung ("Lock-In"-Technik, top-of-fringe stabilization)

Maximum (minimum) stabilization (“lock-in” technique, top-of-fringe stabilization)

Application Reports

Stabilization of an optical cavity with a three-mirror image inverter

A. Kosuge, M. Mori, H. Okada, R. Hajima, K. Nagashima: Stabilization of an optical cavity with a three-mirror image inverter for generation of laser Compton scattered ?-rays. Advanced Solid-State Lasers Congress Technical Digest, OSA 2013 →

“By using a three-mirror image inverter which inverts a phase of the specific polarizing direction, we can obtain an “error signal” to lock a cavity without any transmission element […]. … It can be used successfully to lock the cavity to resonance by means of a digital-based cavity lock system (TEM Messtechnik GmbH).”

Seeding of an OPO for generation of terahertz radiation

D. Molter, M. Theuer, and R. Beigang:
Nanosecond terahertz optical parametric oscillator with a novel quasi phase matching scheme in lithium niobate. →
Optics Express, Vol. 17, Issue 8, pp. 6623-6628 (2009) doi:10.1364/OE.17.006623

“We present an optical parametric oscillator pumped by a single mode Q-switched nanosecond Nd:YVO4 laser for terahertz generation in periodically poled lithium niobate with a new phase matching scheme. This new method leads to an emission of terahertz radiation close to the Cherenkov angle and to a parallel propagation of the pump and signal wave. The emission frequency of this novel source is chosen by the poling period to 1.5 THz. For spectral narrowing the signal wave of the OPO is injection seeded. In the optical spectrum also cascaded processes are observed demonstrating a powerful generation of terahertz waves. The OPO itself is also seeded by a grating stabilized diode laser tunable from 1064 nm to at least 1076 nm. Therefore this seed laser is in principle useful to build OPOs for THz frequencies up to 3 THz when pumped at 1064 nm. For the purpose of cavity length stabilization we apply the Haensch-Couillaud stabilization scheme and a commercially available locking system.”

Tuneable heterodyne infrared spectrometer

G. Sonnabend, M. Sornig, P. Krötz, D. Stupar, R. Schieder:
Ultra high spectral resolution observations of planetary atmospheres using the Cologne tuneable heterodyne infrared spectrometer. →
Journal of Quantitative Spectroscopy & Radiative Transfer 109 (2008) 1016–1029

“High-resolution spectroscopy is a versatile tool to study planetary atmospheres. […] The paper will present a detailed description of the Cologne-based receiver THIS, the only tuneable heterodyne infrared spectrometer for application to astronomy offering access to the 7–17 mm wavelength region at a resolution of up to 3 107 and a bandwidth of 3 GHz.

To optimize the superposition of the signal and the laser and to provide a relative frequency standard a confocal FP ring resonator is used, the so-called diplexer. The diplexer consists of two focusing mirrors (focal length 30 mm) and two highly reflective beam splitters […] The locking process is performed in two steps: first, a stabilized Helium–Neon (HeNe) laser operating at 632 nm […] is fed into the diplexer […] . An error signal is provided by a lock-in amplifier which can then be used to actively control the diplexer resonances via the piezo actuator.

In a second step the transmission of the QCL through the diplexer is monitored via the DC component of the heterodyne detector. A second lock-in/feedback circuit is then used to keep the QCL emission at the maximum of the diplexer transmission curve. Following this procedure the LO can be stabilized in frequency to 1MHz RMS (see Section 2.3). […] The stabilization feedback loop consists of two LaseLock units manufactured by TEM Messtechnik.”

Precision spectroscopy

B Sanguinetti , H O Majeed , M L Jones and B T H Varcoe:
Precision measurements of quantum defects in the nP3/2 Rydberg states of 85Rb. →
J. Phys. B: At. Mol. Opt. Phys. Vol. 42 Nr. 16 pp.165004, 2009 L A M

Johnson, H O Majeed, B Sanguinetti, Th Becker and B T H Varcoe:
Absolute frequency measurements of 85Rb nP7/2 Rydberg states using purely optical detection. →

Tuneable cw-OPO

P. Haag:
Realization and electronical stabilization of diode laser pumped single-frequency continuous-wave optical parametric oscillators based on periodically poled lithium niobate.Doctoral thesis, Technische Universität Kaiserslautern, 2009

Injection-locking of a Ti:Sapphire laser for resonance ionization

Dep. of Quantum Engineering, Nagoya University, Japan and RIKEN Nishina Center, Japan, 2012:
Resonance Ionization Spectroscopy in gas jet using a high repetition rate Ti:Sapphire laser system at SLOWRI PALIS. →

University of Jyväskylä, Finnland, 2013:
Injection-locking of a Ti:Sapphire laser for resonance ionization →

Stabilisierung der Idler-Frequenz eines OPO auf einen Lamb-Dip in Methan →

B. L. Yoder, Steric Effects in the Chemisorption of Vibrationally Excited Methane on Nickel, Springer Theses, DOI: 10.1007/978-3-642-27679-8, Springer-Verlag Berlin Heidelberg 2012

Tobias Lamour, Stanford University (now MPQ Garching) says:
Tobias Lamour, Stanford University says: Taking over the task of locking several cavities with the TEM LaseLock was a difficult but rewarding task. We were able to stabilize systems reliably with unprecedented stability →

Generation of frequency-stabilized cw Terahertz radiation

Francis Hindle, Chun Yang, Arnaud Cuisset, Robin Bocquet, Gael Mouret:
A compact CW-THz spectrometer for applications to gas phase identification and quantification of multiple species →

Rydberg spectroscopy of Rubidium

Precision Laser Spectroscopy of Rubidium with a Frequency Comb. Luke Johnson, PhD thesis, University of Leeds, 2011. Pages 94, 95.

“To study the three-step stabilisation scheme, all three laser steps were stabilised to individual Rb reference cells. The first step laser was stabilised using the polarisation spectroscopy scheme introduced in Section 4.2; this is modulation-free. Active feedback for this laser lock was supplied via the laser cavity piezo and the diode injection current. The second step laser was stabilised using the separate co-propagating setup described in Section 4.3.9; FM was added to the laser via the diode injection current. Feedback for this lock was also supplied via the laser cavity piezo and the diode injection current. The third step was stabilised to a Rydberg signal such as those shown in Figure 5.1 and 5.2. Active feedback for this lock was supplied via the laser cavity piezo only. For all three stabilisation schemes, the error signals were sent through PID controllers and then to the laser drivers for feedback, via universal Laselock units (see Figure 5.4).

[…] With this setup it was possible to stabilise to the Rydberg states […]. In principle all states between these will also be accessible. However, for higher n, the lower SNR of the signals prevented a reliable third step lock. The only limiting factor was the available third step laser power.

The results from this study suggest that the absolute frequencies of Rydberg levels could be measured to an accuracy of <100 kHz using this locking technique. This far surpasses the accuracy of the work in Chapter 4, and would give an accuracy comparable to relative microwave spectroscopy measurements.”

Pricing (EU-Countries):

ComponentsExplanationSingle unit price (EUR)*
LaseLockDigital all-in-one lock box, desktop version, 1x2 PID channels3.995,00
LaseLock 19" 1x2Digital all-in-one lock box, 19”- version, 1x2 PID channels4.795,00
LaseLock 19" 2x2Digital all-in-one lock box, 19”- version, 2x2 PID channels6.690,00
LaseLock 19" 3x2Digital all-in-one lock box, 19”- version, 3x2 PID channels8.585,00
LaseLock 19" 4x2Digital all-in-one lock box, 19”- version, 4x2 PID channels10.480,00
LaseLock DFBLaseLock with DFB laser 780, 795 or 850 nm (others on request)on request
HV ampHigh voltage amp, 2 channels670,00
HV amp 4 channelHigh voltage amp, 4 channels680,00
HC ampHigh current amp, 2 channelson request
DLD-DFBDiode laser driver (current and temp control)1.490,00
LaseLock 24VDigital all-in-one lock box, desktop version, supply voltage 12-24 V DC4.050,00

8 % surcharge for non-European countries plus shipment and possible import duties/taxes in the destination country.

coming soon.