A low-temperature external cavity diode laser for broad wavelength tuning

Abstract

We report on the design and characterization of a low-temperature external cavity diode laser (ECDL) system for broad wavelength tuning. The performance achieved with multiple diode models addresses the scarcity of commercial red laser diodes below 633 nm, which is a wavelength range relevant to spectroscopy of many molecules and ions. Using a combination of multiple-stage thermoelectric cooling and water cooling, the operating temperature of a laser diode is lowered to −64 • C, more than 85 • C below the ambient temperature. The laser system integrates temperature and diffraction grating feedback tunability for coarse and fine wavelength adjustments, respectively. For two different diode models, single-mode operation was achieved with 38 mW output power at 616.8 nm and 69 mW at 622.6 nm, more than 15 nm below their ambient temperature free-running wavelengths. The ECDL design can be used for diodes of any available wavelength, allowing individual diodes to be tuned continuously over tens of nanometers and extending the wavelength coverage of commercial laser diodes.

A Platform for Ultra-Cold External Cavity Diode Lasers

“…in the introduction section (i.e. [4], [5], [19], [20], [21]) reported their designs indicating that for a specific use rather than performance. Mostly their design concentrated on particular atomic transition that is not covered by the readily available coherent sources.…”

“…In order to extend the tuning range of an ECDL system, there are numbers of designs running the laser diodes far from the room temperature down to -45°C [19,20,21]. The list of ultra-cold ECDL system designed is given in Table 1.…”

“…Therefore, as a straightforward approach a water cooling system is to be employed to evacuate the heat dissipated. [4] Vacuum/Vacuum Water cooling -20 [5] Metal Lid/ Nitrogen Water cooling -31 [19] Polystyrene/Atmospheric Air Cooling -45 [20] Plexiglas/Polystyrene Water cooling -31 [21] Vacuum/Vacuum Water cooling -64…”

A simple, powerful diode laser system for atomic physics

“…Also shown are the 780 nm (solid line), 776 nm (dashed line), and 2-photon 778 nm (dotted line) wavelengths, representing transitions in Rb. Note that, in suitably designed systems, extreme temperatures can dramatically extend the tuning range [44].…”

A simple, powerful diode laser system for atomic physics

“…In humid environments with high dew point temperatures 41 , this represents the device's operational limit without compromising diode longevity, but the Rb 2-photon 778 nm transition is already accessible (Fig. 1), and diode wavelength tuning is ≈ 0.3 nm/ • C. By engineering the laser environment 40 dramatic temperature changes can vary available laser wavelengths by 10s of nanometres.…”