EXTENDING RAMAN INTO THE THz REGIME

Transcription

1 Advanced Solutions for Optical Measurements EXTENDING RAMAN INTO THE THz REGIME DELIVERING BOTH CHEMICAL COMPOSITION AND STRUCTURAL INFORMATION IN A SINGLE MEASUREMENT Structural Fingerprint ± 5 cm -1 to 200 cm -1 Chemical Fingerprint 200 cm -1 to 2,000 cm -1 Raman Signal (a.u.) Carbamazepine Raman Shift (cm -1 ) [THz] Form 2 Form 3 Polymorphs and other structural attributes can be clearly identified by strong, low-frequency/ THz-Raman signals Both Stokes and anti-stokes signals from ± 5cm -1 to 200cm -1 (150GHz 6 THz) and beyond! Complete chemical fingerprint

2 SIMULTANEOUS MEASUREMENT OF BOTH CHEMICAL AND STRUCTURAL PROPERTIES Ondax patented 1 THz-Raman systems boost both the efficiency and reliability of materials characterization, in a single, real-time, non-destructive measurement. By unveiling the low-frequency (low wavenumber) range of the Raman spectrum, often referred to as a secondary structural fingerprint, it is possible to directly observe and differentiate key structural properties of materials, while preserving the complete chemical fingerprint. Key applications include: > Differentiation and screening of polymorphs > Monitoring and quantifying degree of crystallinity > Characterizing and observing co-crystal formation > Process monitoring and analysis of chemical reactions > Characterizing thickness and orientation of few-layer nanomaterials > Structural characterization of polymers > Explosives detection and analysis, including determination of formulation methods > Advanced forensic analysis of materials Ondax THz-Raman Spectroscopy Modules are designed as integrated, ultra-compact, plug-and-play solutions to upgrade your existing Raman spectrometer. Comprising an ultra-narrowband ASE-free laser source, NoiseBlock TM 90/10 beamsplitter, and dual-stage SureBlock TM notch filters, the system delivers >OD9 Rayleigh attenuation and signal capture of both Stokes and anti-stokes signals down to 5cm -1. (Fig 2) The THz-Raman region (±5cm -1 to 200cm -1 ) corresponds to the THz-energy vibrations (150GHz-6THz) of inter-molecular/intra-molecular vibrations, including phonon modes, lattice modes, and/ rotational modes. These are often 5-10 times stronger than normal vibrational modes, significantly boosting signal strength. By capturing both Stokes and anti-stokes signals, spectral features can be validated and the excitation wavelength (0cm -1 ) can be precisely determined due to signal symmetry, eliminating the need for system re-calibration. Fig. 1 Benchtop THz-Raman module Narrow-band Dichroic Beamsplitter Ultra Narrow-band Notch Filters ASE Suppression Filters Interchangeable Sample Interface Wavelength Stabilized Laser Fig. 2 THz-Raman spectra of Carbamazepine shows clearly differentiated polymorphic and hydrated forms² Excitation (Rayleigh) Line THz-Raman Fingerprint Region structural chemical THz THz ,000 cm -1 anti-stokes Raman Shift Stokes Ultra-narrow-band Notch Filters & Filter Systems Ondax patented¹ SureBlock ultra narrow-band notch filters are the enabling technology for highly selective wavelength applications like low frequency THz-Raman spectroscopy. With laser line attenuation of up to % (optical density: OD 6) and a transition width of ~5 cm -1, SureBlock TM filters are more than 10 times narrower than available thin-film notch filters. High transmittance on both sides of the notch enables both Stokes and anti-stokes Raman spectra to be simultaneously observed. Designed to fit into standard 1 optical mounts or incorporated into any XLF or TR Series THz-Raman platform, SureBlock notch filters never degrade and are designed for high efficiency and excellent transmission. Available in standard wavelengths of 488nm, 532nm, 633nm, 785nm, 808nm, 976nm and 1064nm, Custom wavelengths available upon request. 1 US Patents 7,986,407 and 8,184,285 2 Data taken using Ondax SureBlock notch filters and a single-stage spectrometer at 785 nm Fig. 3 SureBlock wavelength selectivity at 785nm compared to a thin-film edge filter shows 10x improvement in resolution

3 SYSTEM CONFIGURATIONS All TR-Series THz-Raman modules are ultra-compact and simple to connect via fiber to almost any spectrometer or Raman system. A high-power, wavelength-stabilized, single-frequency laser source is precisely matched to the ultra narrow-band ASE, beamsplitter and notch filters to assure maximum throughput and exceptional attenuation (>OD 9) of the excitation source. Systems are available in 532nm, 633nm, 785nm, 808nm, 976nm and 1064nm excitation wavelengths. The TR-PROBE is a compact, robust THz-Raman probe that enables in-situ reaction or process monitoring, and can also be flexibly configured with a variety of sample interface accessories, including immersion or contact probe tips, a convenient vial/tablet holder, a Transmission Raman adapter, a microscope mount, or a steerable non-contact optic (see options below). A separate CleanLine laser provides ASE-free excitation via a multimode fiber, enabling the probe to operate in harsher environments where electrical connections are not permitted. The TR-BENCH is configured for benchtop use and offers a similar range of interchangeable sample interface accessories holder for fast, easy measurements. The system also comes with a standard cage mounting plate (centered on the collimated output beam) to allow for customized collection optics or easy integration into a customized system. Options include circular polarization or a dual-port/dual polarization output for simultaneous measurement of both S and P polarizations. The TR-MICRO mounts directly to a broad range of popular microscope platforms and micro-raman systems, and can be easily switched in and out of the optical path. Linear polarization is standard, circular polarization is optional. Ondax THz-Raman modules are compatible with virtually any commercial Raman system or spectrometer, and Ondax can recommend or integrate an appropriate spectrometer and deliver as a complete turnkey system. Spectrometer Camera Probe with Vial/Tablet Holder TR-MICRO Probe with Non-Contact Optic TR-BENCH TR-PROBE Probe with Contact/Immersion Probe Tip Probe with microscope mount Probe with Transmission Raman Adapter and sample tablet/vial holders Probe without accessory Collimated beam output A variety of sample interface accessories enable the TR-PROBE and TR-BENCH to be easily configured to match a broad range of applications. Immersion or contact probe tips may be mounted with either a fixed SwageLok mount, or for longer probes that may need alignment, an adjustable tip/tilt probe mount. The Vial/Tablet Sample Holder incorporates an adjustable steering mirror, interchangeable focusing lens, and safety shutter, and the Steerable Non-contact Optic Mount allows for projection and steering of the output beam with precision alignment and interchangeable focusing optics, for applications requiring long-range collection paths. New accessories include a Transmission Raman adapter (Probe only) which s ideal for bulk sampling of tablets or vials, and a Microscope mount with in/out optical switching and beam steering adjustments.

4 Advanced Solutions for Optical Measurements ASE Filters and Beamsplitters The NoiseBlock TM ASE (Amplified Spontaneous Emission) filters and CleanLine TM filter assemblies transmit ASE emission and reflect only the desired single frequency line, suppressing the broadband ASE spectral background of a single frequency laser by >40dB resulting in a clean, ASE-free beam (Fig. 1). NoiseBlock TM filters ensure the pure spectral excitation beam required for ultra-low frequency THz-Raman spectroscopy and other demanding applications. They are designed to match the ultra-narrow spectral profile of our SureBlock Notch Filters, and are incorporated into all Ondax TR Series THz-Raman Systems. They can also be used as spectrally selective 90/10 Beamsplitters, providing up to a 4x throughput improvement in Raman spectroscopy applications. Available from 400nm to 2000+nm, in free-space, fiber-coupled, and pre-assembled CleanLine TM configurations. Fig. 1 Wavelength stabilized laser ASE VHG Filter Transmitted ASE light Specular reflection Mirror or 2nd ASE VHG Filter ASE filtered laser beam Integrated LM Module and CleanLine ASE Filter assembly Free space ASE and 90/10 Beamsplitter or standalone CleanLine ASE Filter Assembly Raw laser diodes produce ASE light on the order of 40-60dB below the laser line that can affect critical measurements within cm -1 of the laser line. NoiseBlock TM filters efficiently suppress ASE, leaving a spectrally pure source for measurements down to <10cm -1. Typical performance is shown at right for a 405nm and 785nm lasers. WAVELENGTH STABILIZED DIODE LASERS The majority of modern Raman spectroscopy systems depend upon wavelength stabilized diode laser technology pioneered by Ondax. The Ondax PowerLocker, a miniature, ultra-narrowband Volume Holographic Grating (VHG) filter, creates an external cavity that locks the diode laser wavelength into a narrowed optical spectrum. This increases spectral brightness and delivers the stabilized optical performance required for precise, repeatable Raman measurements. All SureLock Wavelength Stabilized Laser Diodes and Laser Modules incorporate the PowerLocker and are engineered for optimum Raman performance. Available in a wide range of wavelengths, power levels, and form factors, Ondax can also custom-configure a wavelength-stabilized solution to meet your exact application or OEM requirements for any Raman spectroscopy system. BENCHTOP TURNKEY MODULES WAVELENGTH STABILIZED LASERS 405NM TO 1064NM OEM SOLUTIONS COMPONENTS

5 ADDITIONAL APPLICATIONS Crystal Monitoring and Analysis Identifying and monitoring the formation of cocrystals is also improved using THz-Raman spectra. The figure above shows the clearly recognizable peak shifts that occur when cocrystals are formed in a mixture of Caffeine and 2-Benzoic acid. Phase Monitoring Phase changes of Sulfur observed when heated from room temp.(α) to 95.2 C (β) and then to the melting point of C (λ). Note the clearly recognizable changes in peak location, shape and magnitude in the THz-Raman region. Crystalline phases result in sharp peaks, which broaden and dissipate as the sulfur liquifies. Gas Sensing Rotational modes of many gases can be clearly seen in the THz-Raman region. Signal intensities can be up to 10x those in the fingerprint region, opening up the possibility of using Raman for extremely sensitive gas sensing applications. The Stokes/anti- Stokes ratios can also be used for in situ sensing of temperature. Phase Monitoring Low frequency spectra can be used to monitor transformation of polymorphs. The waterfall plot above shows anhydrous theophylline before and after its transformation into a flocculated slurry, over a period of approximately 100 seconds. Data courtesy Clairet Scientific Ltd. Polymorph Identification Polymorphic forms and hydrates of pharmaceuticals can easily be distinguished in raw materials analysis, finished goods, process monitoring, and QC applications. Synthetic Pathway Analysis - Explosives Forensics Multiple samples of ETN (Erythritol Tetranitrate), representing systematic variations of ingredients and preparation routes, show distinctive differences. Visit the Ondax Online Store to find off-the-shelf samples of hundreds of products, available for immediate delivery. For more information about Ondax products and the name of a local representative or distributor, visit sales@ondax.com, or call

6 ADDITIONAL APPLICATIONS Pharmaceutical Applications Key challenges for the pharmaceutical industry includes polymorph identification, reaction monitoring, raw material quality control, and counterfeit detection. THz-Raman reveals structural fingerprints that can rapidly differentiate polymorphs, isomers, co-crystal, and other structural variations of substances and compounds. Explosives Detection, Forensics and Source Attribution THz-Raman goes beyond chemical detection to reveal a structural fingerprint that can be attributed to specific ingredients, methods of manufacture, and storage/handling of many popular home-made explosive (HME) materials, revealing clues about how and where they were formulated. Semiconductor and Nanomaterials Graphene and carbon nanotubes are just two of the many nanomaterials that exhibit strong low-frequency signals. For Graphene, THz-Raman analysis can determine the number of monolayers, and for carbon nanotubes, the diameter of the structure. Differences in structural characteristics and defects in crystals can also be detected. Crystallization and Reaction Monitoring Low-frequency THz-Raman signals undergo clear, rapid shifts corresponding to changes in molecular structure, enabling highly sensitive, real-time monitoring of crystal form, phase, or structural transformations. Industrial and Petrochemical THz-Raman delivers additional sensitivity and information about molecular structure to control processes, improve yields, and monitor crystallization or structural transformation during manufacturing. Gas Sensing Rotational modes of gases such as Oxygen provide signal intensities up to 10x those in the fingerprint region. Stokes/anti-Stokes ratios can also be used for remote sensing of temperatures in gases, plasmas, liquids and solids. Visit the Ondax Online Store to find off-the-shelf samples of hundreds of products, available for immediate delivery. For more information about Ondax products and the name of a local representative or distributor, visit sales@ondax.com, or call E. Duarte Rd. Monrovia, CA (Tel) (Sales Fax) No responsibility is assumed by Ondax, Inc. for use of this product nor for any infringements of patents and trademarks or other rights of third parties resulting from its use. No license is granted under any patents, patent rights or trademarks of Ondax, Inc., and the company reserves the right to make changes in specifications at any time without notice. Each purchased laser is provided with test data. Please refer to this data before using the laser Ondax, Inc.