Lastek: Photonics Technology Solutions

Asynchronous optical sampling (ASOPS) is a method for time domain spectroscopy on ultrashort time scales which does not rely on a mechanical delay stage and thus enables scan rates in the kilohertz regime. Laser Quantum’s ASOPS technology has been developed and improved over 15 years for applications in spectroscopy using femtosecond lasers. The first commercial ASOPS system has been released to the market in 2005. Since 2010, the 3rd generation stabilisation unit based on the patented DDS technology (direct-digital-synthesis, DDS) has emerged, ensuring a time resolution better than 50 fs over a full scan range of 1 ns when used in combination with two 1 GHz Ti:Sapphire laser systems. When employing ASOPS there is a small difference in the repetition rate of the pump and probe lasers respectively, which leads to a difference in the pulse-to-pulse separation between pump and probe laser beams which increases linearly with Δt= ΔfR/fR2. TheASOPS Engine consists of two femtosecond laser systems with almost identical repetition rates, the patentedTL-1000 ASOPS stabilisation unit and a fast acquisition card for high-speed measurements. The ASOPS Engine has been available so far with only the 1 GHz taccor laser range, and is now also available with theventeon and gecco laser series which run at a repetition rate of 84 MHz.

The two femtosecond lasers are working in a master slave configuration in which the repetition rate of the slave laser is controlled to be equal to the master laser repetition rate up to a small offset using a phase locked loop. The difference between the repetition rates depends on the lasers employed and typically is 100 Hz (for 84 MHz) up to 10 kHz (for 1 GHz systems). For specific purposes, the TL-1000 ASOPS unit supports values even beyond those between 4 µHz and 20 kHz. The difference frequency can be easily controlled using a touch screen. The lock procedure between the lasers employed is achieved using a push button. Laser Quantum’s patented stabilization electronics enables a very high time resolution over the complete measurement window and enables the highest time resolution values on the market today.

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Coherent anti-Stokes Raman scattering (CARS) spectroscopy primarily was used in chemistry, physics and related fields. It is sensitive to the same vibrational signatures of molecules as seen in Raman spectroscopy, typically the nuclear vibrations of chemical bonds. Unlike Raman spectroscopy, CARS employs multiple photons to address the molecular vibrations, and produces a signal in which the emitted waves are coherent with one another. As a result, CARS is orders of magnitude stronger than spontaneous Raman emission. CARS is a third-order nonlinear optical process involving three laser beams: a pump beam of frequency ω pump , a Stokes beam of frequency ω Stokes and a probe beam at frequency ω probe. Read more. 

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The Ekspla Sum frequency generation (SFG) spectrometer is based on picosecond pump laser and optical parametric generator (OPG) with difference frequency generation (DFG) extension. Solid state mode-locked Nd:YAG laser featuring high pulse duration and energy stability is used in the system. Fundamental laser radiation splits into several channels in multichannel beams delivery unit. Two of these beams are used for pumping OPG and DFG. Small part of laser output beam, usually with doubled frequency (532 nm), is directed to VIS channel of SFG spectrometer. IR channel of spectrometer is pumped by DFG output beam. All system components are designed to operate in tandem. The sizes of individual compartments, positions of apertures and beams heights are fitted. As a result SFG spectrometer takes less space in laboratory. Standard versions usually fit on 1000×2400 mm optical table. No laser beams are passing across optical table. For example beam dedicated for VIS channel passes through OPG compartment only to minimize the risk of accident with dangerous high intensity laser radiation. It makes Ekspla spectrometer substantially safer comparing to home-made SFG-VS setups. Also optical parameters, like beam diameter, pulse energy, delays between channels are perfectly matched. We designed our spectrometer thinking about user friendly operation. Read more. 

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