Diode Lasers and Electronics

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1 Diode Lasers and Electronics High Performance External cavity diode laser Laser controller Laser accessories Precision and flexibility 1

MOGLabs MOGLabs is a company of in-the-lab scientists and engineers, people that know what you need because they ve come from labs just like yours.

MOGLabs is dedicated to bringing you outstanding electronics to control your diode laser, and lasers that just work. Outstanding in quality, performance, ease of use and price.

We Our Products The DLC series laser controllers are our flagship product, affectionately knows at the MOGbox. What makes the MOGbox special?

It's all analogue, both for the superior noise performance and the quick access to critical controls.

The diode current noise is the lowest available, both as measured directly in pa/ Hz and more importantly where it matters most, in the laser linewidth.

2 MOGLabs MOGLabs is a company of in-the-lab scientists and engineers, people that know what you need because they ve come from labs just like yours. We bring you products which carefully balance features, design and ergonomics. hope that you will quickly take our products for granted in your lab, because they just work the way you need them to. MOGLabs is dedicated to bringing you outstanding electronics to control your diode laser, and lasers that just work. Outstanding in quality, performance, ease of use and price. Our products are the result of years of active laboratory development by research students and scientists using diode lasers all day every day. We Our Products The DLC series laser controllers are our flagship product, affectionately knows at the MOGbox. What makes the MOGbox special? Ease-of-use is critical: all the things you need to control and lock a single-frequency diode laser are in one compact box. It's all analogue, both for the superior noise performance and the quick access to critical controls. But we know our users care most of all about the performance, and in particular stability and noise. The diode current noise is the lowest available, both as measured directly in pa/ Hz and more importantly where it matters most, in the laser linewidth. And best of all, the cost is remarkably low: for not much more than the price of a simple current and temperature controller, you can have both ac and dc feedback locking, in-built phase-sensitive detector (lock-in amp), two high-voltage piezo actuator drivers, high-current modulator driver, and high-speed low-noise differential photodetector. Even if you don't need all that, you will still benefit from the lower noise and improved ergonomics. to acoustic disturbances. It is designed to use low-cost readily available laser diodes, rather than expensive and inaccessible AR-coated diodes, yet achieves sub-100khz linewidth and tens of GHz modehop-free continuous scan range. There are now MOGLabs products in dozens of labs around the world, in Australia, Britain, Bulgaria, Canada, China, France, Germany, Malaysia, the Netherlands, Russia, Scotland, Singapore, South Africa, South Korea, Sweden, Thailand, the United States, United Arab Emirates, and Vietnam. But even the very first MOG box, the Mark 1 prototype, is still in operation, running a laser in a cooling and trapping laboratory at the University of Melbourne. Following the success of our electronics, we introduced a series of external cavity diode lasers. The latest version is built around a laser cavity machined from a solid monolithic block, which provides excellent thermal stability and immunity 2

External Cavity Diode Laser ECD-003 The MOGLabs external cavity diode laser offers research quality at a teaching-lab price.

after day, so you can concentrate on your research.

using a low-cost uncoated 780 nm consumer diode.

3 External Cavity Diode Laser ECD-003 The MOGLabs external cavity diode laser offers research quality at a teaching-lab price. Model EDC-003 is a Littrow-configuration design machined from a solid monolithic block of metal, making it robust, stable and insensitive to external vibrations. The laser is shipped on-resonance (for Rb and Cs wavelengths) and after a short warm-up each morning, you can expect the laser to return to resonance day after day, so you can concentrate on your research. The performance is excellent when used with a MOGLabs Diode Laser Controller, with modehop-free scanning range of up to 30 GHz and linewidth below 100 khz using a low-cost uncoated 780 nm consumer diode. The design is modular and user-accessible, to allow for changing research needs and simple, convenient end-user replacement of the laser diode and other components. Features Benefits Wavelengths from 370nm to 1550nm Power up to 120mW Solid monolithic block cavity design Precision alignment controls Microwave RF modulation input Diode protection circuit and relay User accessible High performance, low cost Excellent passive stability Modehop-free tuning up to 30GHz Narrow linewidth Low frequency noise High feedback bandwidth Reconfigurable 3

External Cavity Diode Laser Specifications ECD-003 Wavelength/frequency 780nm standard Linewidth RF modulation Grating Coarse tuning range Optical Beam characteristics Polarisation Thermal TEC Sensor

4 External Cavity Diode Laser Specifications ECD-003 Wavelength/frequency 780nm standard Linewidth RF modulation Grating Coarse tuning range Optical Beam characteristics Polarisation Thermal TEC Sensor Stability at base Cooling Sweep/scan Scan range Mode-hop free scan Piezo Cavity length Electronics Protection Indicator RF input Connector Dimensions Dimensions 50mW to 120mW output power, diode dependent Typically <300kHz FWHM 2.5GHz bandwidth Standard: 1800 l/mm gold coated ±5nm for single diode; 700nm to 860nm with different diodes 4mm 1.5mm (1/e 2 ) typical; diode dependent Vertical linear 100:1 typical ±14.5V 3.3A Q = 23W standard NTC 10k standard; AD590, 592 optional ±1mK (controller dependent) Water cooling connections optional (usually not required) 25 GHz typical, with MOGLabs controller 10 GHz typical, uncoated diode, with current feed-forward 0 150V, 4.8μm, resonance at >1kHz with std grating 1 3cm (5 15 GHz FSR) approx. Relay, cover interlock connection, reverse diode Laser ON/OFF (LED) 16MHz 2.5GHz bias tee (lower cutoff optional) MOGLabs DLC Diode Laser Controller (single cable connect) 122 x 94 x 70mm (LxWxH), 1kg 4

External Cavity Diode Laser Options Anti-reflection coated diodes For most applications, our standard laser diodes with lowreflectivity coating on the external facets are satisfactory.

power cannot be arbitrarily varied. The mode-hop-free tuning range is then typically 15GHz to 30GHz, with current bias enabled.

5 External Cavity Diode Laser Options Anti-reflection coated diodes For most applications, our standard laser diodes with lowreflectivity coating on the external facets are satisfactory. However, the injection current must be adjusted so that the internal diode cavity frequency and external cavity mode frequency are matched for the preferred laser output frequency, and the output power cannot be arbitrarily varied. The mode-hop-free tuning range is then typically 15GHz to 30GHz, with current bias enabled. Current bias refers to varying the laser current automatically as the frequency is scanned. Ultra-low reflectivity coatings on the diode allow continuous frequency tuning without mode-hops, or continuous variation of the output power, over a larger range. Such diodes are available at a range of wavelengths and power ratings. Fold mirror When tuning the laser wavelength by rotating the grating, the output beam direction will change. This can be corrected with a fold mirror. During operation, the MOGLaser output beam direction does not change with frequency, only when manually adjusting the grating angle. Thus for most applications, the fold mirror is not required and degrades the performance (increases susceptibility to vibration). If you will be working at one wavelength (e.g. the Rb D2 line) then we recommend against this option. Hermetic seal The laser cavity can be hermetically sealed with the addition of cavity exit windows and o-ring seal. The sensitivity to the effects of drafts and noise will be reduced. Condensation due to operation at low temperatures will also be minimised inside the cavity. Note that the seal is not vacuum tight. Liquid cooling The laser base has a liquid cooling channel. Liquid cooling is normally not necessary, but we offer quick-fit connectors to allow easy connection if required, for example to cool the laser substantially below room temperature. Faraday isolator External cavity diode lasers are extremely susceptible to optical feedback, and require some form of optical isolation for stable single-frequency operation. We offer a Faraday isolator from EOT with 4mm diameter aperture, typically 37dB isolation and 85% transmission. Diffraction gratings We use gold-coated sinusoidal holographic gratings, with diffraction efficiency chosen to balance frequency stability and output power. Lower efficiency gratings increase the output power by up to 20%, provided the operating wavelength is close to the diode gain peak wavelength, and at the expense of reduced mode-hop-free scan range. Alternately, higher diffraction efficiency may be needed to pull the lasing wavelength far from the diode gain peak. Headboard and cable These are normally included with the MOGLabs DLC controllers. If the laser is purchased separately without controller, these will be required. Bases Non-magnetic stainless steel bases are available to raise the laser beam height and provide a large mass to reduce the influence of acoustic vibrations. 5

6 External Cavity Diode Laser Performance Frequency noise and linewidth Frequency noise is jitter in the frequency of the laser light output. Lasers are remarkably sensitive to variations in temperature, pressure and cavity length: just one nanometre change in cavity length causes a laser frequency shift of 25 MHz. The ECD-003 is machined from a solid block of alloy to reduce the effects of acoustic vibration, to increase thermal stability, and to seal the cavity against air pressure drifts. The ultimate test of the laser frequency noise is the linewidth, which depends on cavity stability and alignment, grating feedback efficiency, and properties of the semiconductor diode. The beatnote spectrum at right shows the laser linewidth, measured using a delayed selfheterodyne technique. In combination with the extremely low current noise of the MOGbox electronics, the laser linewidth is routinely below 100 khz (FWHM). Modehop-free tuning range There are competing wavelength-selecting effects in a Littrow configuration diode laser, including the intrinsic laser diode cavity, the external cavity, and the diffraction grating. As the laser frequency is scanned, these effects compete and the laser can hop between external modes. The MOGLabs laser can tune up to 30 GHz without a mode-hop, using a standard low-cost uncoated diode. 6

Diode Laser Controller DLC-202/252/502 The MOGLabs diode laser controller ( MOGbox ) provides everything needed to drive a tuneable external cavity diode laser and lock it to an atomic or other

It offers a combination of impressive performance and easeof-use: ergonomic and low-noise analogue controls, and intuitive front-panel selection of the signals you need to monitor.

7 Diode Laser Controller DLC-202/252/502 The MOGLabs diode laser controller ( MOGbox ) provides everything needed to drive a tuneable external cavity diode laser and lock it to an atomic or other frequency reference. It offers a combination of impressive performance and easeof-use: ergonomic and low-noise analogue controls, and intuitive front-panel selection of the signals you need to monitor. The diode current noise is the lowest available, both as measured directly in pa/ Hz and more importantly where it matters most, in the laser linewidth. The narrow laser linewidths achieved with MOGLabs electronics and lasers demonstrate the low current noise, and also the equally critical low noise on the piezo drive, where even microvolts matter. Features Eight functions in one unit: Ultra low noise current source Temperature controller Photodetector Demodulator (lock-in amplifier) Feedback servos Two high voltage piezo drivers Modulator driver Sweep ramp generator Benefits Compact, high performance, low cost Ergonomic design o Real analogue controls, no irritating up/down push-button switches o Intuitive controls, logarithmic response o Quick selection of signals to monitor o Two oscilloscope trace selector switches o Auto-lock to centre of scan o All cables at rear Use with MOGLabs laser or your own 7

8 Diode Laser Controller Specifications DLC-202/252/502 Rev 6.0 Current Output current Noise External modulation Compliance voltage Temperature Range Stability TEC power Sensor DLC-202: 0 200mA,±10μA display resolution DLC-252/502: 250mA/500mA,±100μA display resolution Below 300pA/ Hz 0 100kHz ( 3dB), 100μA/V, plus direct RF, to 2.5GHz ( 3dB) Max diode voltage 3.2V@200mA, 6V@100mA; optionally higher 0 30 C ( 40 C to 50 C optional), ±0.1 C display resolution ±5mK/ C ±2.5A, ±9V (22W) NTC 10k (provided) Alternately AD590, AD592, auto-detected; reads C in all cases Photodetector Photodiodes Si-PIN, nm, lensed ±10 ; options: nm, ±20 Bandwidth 720kHz ( 3dB); CMRR >120dB Coupling ac (differential pair); dc Dimensions 30 x 30 x 60mm (approx) Frequency feedback servos Modulation 250kHz ± 20kHz; current driver output ±500mA ±8V Bandwidth 40kHz typical (laser-dependent) Phase Feedback Double integrator (slow, piezo) + single integrator (fast, current) Gain ±20dB master plus ±20dB on slow, fast channels Sample and Hold External control of lock/sweep; allows frequency jump and relock Sweep/scan Sweep Piezo output Range Power and dimensions IEC input IEC output Dimensions Scan rate 4Hz to 70Hz 0 150V, 5mA, 2 channels; stack output limit can be set to 120V Typically 10 to 30GHz, laser dependent 110/120 or 220/240V, 50/60 Hz, 3A Common ground with input 19 2U, 88 x 422 x 210mm (H x W x D), 4.3kg Package contents 1. DLC-xx2 laser control unit 4. Laser head/diode connection/protection board with SMA RF input 2. PDD-001 photodetector 5. Mounting plate for laser head board 3. Manual 6. Cables (power, laser, photodetector), 10k NTC thermistor 8

Diode Laser Controller Options High compliance voltage For standard DLC controllers, the maximum voltage available to the laser diode is 6V at 100mA and 3.2V at 200mA.

A high compliance voltage version of the MOGbox is available as an option. Extended temperature range The default temperature range is 0ºC to 30ºC, with a safety cutoff limit of 5ºC.

Photodiodes The default photodetector includes filtered photodiodes, sensitive from 750 to 1100nm, with narrow viewing angle (±10º).

Photodiodes are available to cover the UV, visible and mid-ir spectrum, and/or with wider viewing angles of ±20º or ±75º.

MOGLabs can provide a mechanical mounting plate, with machined holes for the main connector, LED indicator lamp, and RF injection SMA connector.

9 Diode Laser Controller Options High compliance voltage For standard DLC controllers, the maximum voltage available to the laser diode is 6V at 100mA and 3.2V at 200mA. Most laser diodes, including blue, violet and UV diodes, can be driven with a standard DLC but as higher-current blue and UV devices become available, higher voltages may be required. A high compliance voltage version of the MOGbox is available as an option. Extended temperature range The default temperature range is 0ºC to 30ºC, with a safety cutoff limit of 5ºC. The range and safety limit can be altered in the factory if required. The temperature range and limit can also be altered by the end-user via minor resistor changes. Photodiodes The default photodetector includes filtered photodiodes, sensitive from 750 to 1100nm, with narrow viewing angle (±10º). These are inherently insensitive to laboratory lighting and sunlight, and the narrow viewing angle further reduces background noise. Photodiodes are available to cover the UV, visible and mid-ir spectrum, and/or with wider viewing angles of ±20º or ±75º. Laser headboard mounting plate The MOGLabs electronics includes a laser headboard with protection circuits, RF bias tee, and breakout connectors to make it easy to connect your laser. MOGLabs can provide a mechanical mounting plate, with machined holes for the main connector, LED indicator lamp, and RF injection SMA connector. Two types are available: a direct replacement for the endplate of a Toptica DL 100 laser, or a simpler laser-cut anodised aluminium rectangle (76x47x2mm). Laser headboard Additional laser headboards are useful if you have multiple lasers for each MOGbox controller. Laser cable Additional MOGbox-to-laser cables can be purchased. They are standard 2m long DVI-D dual-link cables. You can obtain such cables elsewhere, but please be careful to specify duallink, and note that we have observed substantial ringing oscillations with cheap cables. Digital oscilloscope A two-channel oscilloscope is essential for scanning and locking. We can provide a very low-cost two channel colour digital oscilloscope. Atomic and molecular vapour cells The MOGbox is designed to lock a tuneable laser to an atomic transition. MOGLabs can provide a wide range of atomic and molecular reference cells; please refer to the Accessories section of this catalogue. Zeeman coil and mount AC (centre of line) locking is easy with a MOGbox, for example by modulating the injection current. However, the linewidth is then increased. The MOGbox can also directly drive a coil around a vapour cell, to modulate the atomic resonance. MOGLabs can provide a PCB with vapour cell, coil and impedance balance circuitry. 9

10 Diode Laser Controller Performance Current noise The frequency of light from a laser diode is extremely sensitive to current, about 3 MHz/μA. To achieve the 100 khz linewidth desired for laser cooling of atoms, the current noise must be lower than 30 na. The MOGbox design is steadfastly analogue, with no digital clock signals. The power supplies are all linear, rather than switchmode. The transformer is toroidal to minimise external AC magnetic fields through the PCB, with an additional layer of magnetic shielding to further reduce fields. The DC voltage supplies are each filtered and regulated then filtered and regulated again. Sensitive signals on the 10-layer PCB are run along inner layers with Faraday shielding copper on other layers around them. The current noise is very nearly too small to measure: 150 dbm/ Hz, i.e. below 100 pa/ Hz. No other laser diode driver has demonstrated such low noise, and using a MOGbox, we have measured laser linewidths of 35 khz (rms). Frequency stabilisation The MOGbox includes a three-channel frequency feedback servo system (current, slow piezo and fast piezo). In combination, more than 80dB of suppression is possible at low frequencies, with bandwidth up to 40kHz. Higher bandwidth is readily achieved using external error signal, up to 10MHz via external modulation and 3GHz with the in-built RF bias-tee. Ref -70 dbm -70 * Att 5 db * RBW 1 Hz AQT 1000 s mA 50ohm 0mA 50ohm Stability The temperature and current controllers use low temperature coefficient references which are temperature-controlled, and the enclosure has a temperature-controlled fan to keep components within a limited temperature range. Lasers stay close to resonance even without locking, so you can concentrate on doing your experiments Center 500 khz 100 khz/ Span 1 MHz 10

Accessories Atomic and molecular vapour cells MOGLabs stocks popular used vapour cells, manufactured by our US partners, Triad Technology.

We can also supply cells with optically contacted windows (imaging quality), quartz cells, and cells with isotopically pure Rb85 or Rb87, sodium, potassium, iodine, and molecular gases such as

Shutter driver The voice coil actuator from a hard disc can be used as a very fast (sub-microsecond) mechanical shutter for laser beams (Enhanced laser shutter using a hard disk drive voice-coil

11 Accessories Atomic and molecular vapour cells MOGLabs stocks popular used vapour cells, manufactured by our US partners, Triad Technology. These include standard rubidium (natural isotopic mix) and caesium cells, 75mm length x 25mm diameter. We can also supply cells with optically contacted windows (imaging quality), quartz cells, and cells with isotopically pure Rb85 or Rb87, sodium, potassium, iodine, and molecular gases such as acetylene, hydrogen cyanide, carbon monoxide, and methane. Shutter driver The voice coil actuator from a hard disc can be used as a very fast (sub-microsecond) mechanical shutter for laser beams (Enhanced laser shutter using a hard disk drive voice-coil actuator, Rev. Sci. Instrum. 78:026101, 2007). The MOG- Labs shutter driver includes both manual toggleswitch and TTL control, and will drive a forward or reverse current, up to 6 amps at up to 55 volts, requiring only a standard single-polarity wall-wart plugpack power supply. Faraday isolators External cavity diode lasers are extremely susceptible to optical feedback, and require some form of optical isolation for stable singlefrequency operation. We offer Faraday isolators from EOT with 4mm diameter aperture, typically 37dB isolation, 85% transmission. Also available with prism polarisers for injection locking applications. Waveplates We stock a select range of low-order AR-coated quartz waveplates, λ/2 and λ/4, at 780nm and 852nm. They are very competitively priced, with 15mm clear diameter in 25.4mm ring mounts. They are perfect for saturated absorption spectroscopy arrangements for frequency stabilization of MOGLabs lasers. MOGLabs photodetector The photodetector supplied with MOG controllers is available separately. In standard configuration, it provides a balanced differential Si-PIN photodiode pair, with 720 khz bandwidth (-3dB), a good signal with just 20μW illumination, and very low noise. Standard diode options include nm or nm (solar blind) sensitivity, ±10, 20 or 75º field of view. Dimensions are 68 x 30 x 30 mm. Laser diodes We can provide additional laser diodes for MOGLabs customers. We commonly stock diodes at 780nm/90mW, 780nm/150mW with very low reflectivity front-facet coatings (<0.25%), 795nm/150mW and 852nm at 150mW. Other wavelengths are available by arrangement. 11

MOG Laboratories Pty Ltd 420 Victoria St Brunswick VIC 3056 AUSTRALIA Tel: +61 3 9940 1427 Fax: +61 3 9381 0700 info@moglabs.

com Triad Technology 640 South Sunset Street Longmont, CO 80501 USA Tel: +1 720 494 0717 Fax: +1 720 306 3716 sales@triadtechno.

com Rhysics Photronics Rhysics Photronics 341 Hanshin S-MECA, 1359 Kwanpyung-Dong Yuseong-Gu Daejeon 305-509 Korea Tel: +82 42 671

12 MOG Laboratories Pty Ltd 420 Victoria St Brunswick VIC 3056 AUSTRALIA Tel: Fax: info@moglabs.com Triad Technology 640 South Sunset Street Longmont, CO USA Tel: Fax: sales@triadtechno.com Rhysics Photronics Rhysics Photronics 341 Hanshin S-MECA, 1359 Kwanpyung-Dong Yuseong-Gu Daejeon Korea Tel: Fax: sclee@rphotronics.com Rexco Hanoi No. 13 Lot 12A Trung Hoa Str Cau Giay Dist Ha Noi Vietnam Tel: Fax: cta.sales@rexco.com.vn MOG Laboratories Pty Ltd t: info@moglabs.com Victoria St Brunswick VIC 3056 Australia f:

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