The design of the externalcavity diode laser presented here takes advantage of a simple modi. Developing an electronically controlled external cavity diode. Pdf grating stabilized external cavity diode lasers for raman. Interference lter stabilized external cavity diode laser. A semiconductor laser diode ld with a central wavelength of 698 nm is anti reflection coated on its output facet and is combined with an external cavity, leading. Painter california institute of technology abstract anenhancedtunablelittrowcon. A series of experiments are performed to characterize the light emitted from an external cavity diode laser. This diode was placed in an external optical cavity. Mar 20, 2020 the vertical cavity surfaceemitting laser, or vcsel, is a type of semiconductor laser diode with laser beam emission perpendicular from the top surface, contrary to conventional edgeemitting semiconductor lasers which emit from surfaces formed by cleaving the individual chip out of a wafer. The mechanical design of the external cavity laser is shown in fig. Characterization and development of an extended cavity tunable laser diode by fnu traptilisa approved for the department of physics and astronomy san jose state university may 2014 dr. A semiconductor diode laser having a modified littrow external resonator is described. Aug 09, 2010 diodenlaser 405nm, sfaw210 mit externem resonator mit littrowaufbau. In this paper, we derive a model capable of describing multicavity laser systems with polarizationdependent elements.
The verticalcavity surfaceemitting laser, or vcsel, is a type of semiconductor laser diode with laser beam emission perpendicular from the top surface, contrary to conventional edgeemitting semiconductor lasers which emit from surfaces formed by cleaving the individual chip out of a wafer. We report a homebuilt external cavity diode laser ecdl, using a diode whose front facet is not anti reflection ar coated, that has a modehopfree mhf. An external cavity has been developed for use with commercial diode lasers. Pdf two simple external cavity diode laser designs using fibre pigtailed gain chips are tested and their properties compared with a high end dbr fibre. Recently, we have demonstrated large modehop free tuning of an external cavity diode laser with an offtheshelf laser diode. This configuration allows a gaalas diode laser to be tuned conveniently anywhere in a range greater than 20 nm. Due to the arcoating on the laser diode, there is just a weak resonator in the bare laser diode. Tunable highpower externalcavity gan diode laser systems in. Frequency locking of an external cavity diode laser. This novel approach employs a closedloop control based on polarization spectroscopy.
The use of two external cavity diode lasers allows the implementation of a twostep procedure which combines the length measurement with a variable synthetic wavelength and its interpolation with a fixed synthetic wavelength. The output power is coupled out via the rear facet of the laser chip for avoiding any beam walk. A constant current source for an external cavity diode laser. An absolute distance interferometer with two external. Narrowbanded ecl lasers are characterized by a very small line width, low noise, and very good wavelength stability. New patent cd for external cavity laser with rotary tuning element. Driven by voltage, the doped pntransition allows for recombination of an electron with a hole. Tunable external cavity diode lasers world scientific. The ecdl, which was namedpromisefigure3,consistsofa70mw,785 nm laser diode sanyo dl7140201s and aspheric. However, our novel transmission grating can be used directly in the littrow configuration which leads to compact and simple mechanical structure and reduces losses inside the cavity. The laser will oscillate at a wavelength resonant with the external laser cavity between the diode rear facet and the grating. The centre wavelength can be preadjusted within the tuning range of 20 nm. The light emitted from the diode dl is collimated by an objective lens lc with short focal length 3 to 4. The external cavity is realized with class d antireflection coated diode lasers and with a high efficiency diffraction grating.
The obtained results can be used as a guide for selecting gratings for externalcavity diode lasers for diferent requirements. Diode lasers unlike leds will not operate below a threshold current. Modehopfree tuning over 140 ghz of external cavity diode. Vcsels are used in various laser products, including. A laser diode, ld, injection laser diode ild, or diode laser is a semiconductor device similar to a lightemitting diode in which a diode pumped directly with electrical current can create lasing conditions at the diodes junction 3 laser diodes can directly convert electrical energy into light. A diode laser is simply a light emitting diode led with a feedback cavity. Scholten1, 1arc centre of excellence for coherent xray science, school of physics, the university of melbourne, victoria 3010, australia 2school of physics, monash university, victoria 3800, australia corresponding author. These two parameters are well suited for roughly 7. But it is interesting to look at the characteristic curve to. Modehopfree tuning over 140 ghz of external cavity diode lasers. The former devices are sometimes referred to as injection laser diodes to distinguish them from optically pumped laser diodes.
This is another external cavity with a simple diode laser of 1w 445nm working at low power for view the phenomen of external resonant. Osa model for tuning an externalcavity diode laser by. An additional output coupling mirror in a vshape configuration of the resonator makes the system more efficient and convenient to operate. This results in the best performance for an external cavity diode laser system in littrow. In this project we have created an external cavity diode laser ecdl, which selects a single wavelength from the entire output spectrum of the diode laser and drives the laser at this wavelength. Thus, by using optical feedback from a diffraction grating, we are able to narrow the total bandwith. The laser is first prestabilized to a simple optical cavity with finesse of 10,000.
Pdf external cavity diode lasers with 5khz linewidth and 200nm. Next we use interferometry to make a precise measurement of the central wavelength. A gratingtunable externalcavity laser based on a semiconductor laser diode a thesis for the degree of master of science presented to dublin city university by brian kevin hurley b. Stabilizing diode lasers to h ighfi n esse cavltl es fox. The lens is chosen to compensate for abberations arising from the diodes packaging window. Design of external cavity semiconductor lasers to suppress wavelength shift and mode hopping l. An external cavity diode laser sensor article pdf available in journal of lightwave technology 11. Osa externalcavity diode laser using a grazingincidence. Ramendra bahuguna department of physics and astronomy dr. Characterization and development of an extended cavity. This book will appeal to undergraduate and graduate students, scientists and engineers alike.
A multimode diode laser with an external cavity is studied experimentally and theoretically for its application to intracavity spectroscopy. Compact, thermalnoiselimited optical cavity for diode laser. Aosense has developed a line of external cavity diode lasers ecdls designed to meet. Also, the linewidth is reduced by a factor of more than from 40 mhz to less than 10 khz. An externalcavity laser has been described where the problem of obtaining sufficient diffraction back to the laser is circumvented by using a combination of an ordinary transmission grating and a mirror. Manual tunable littrow laser system lynx s3 sacher laser. External cavity diode lasers yield stable output frequency and narrow spectral bandwidth by exploiting the sensitivity of diode lasers to external optical feedback. The gan laser diode dtr laser shop, m462 used in the experiment is a 2 w broadarea diode laser emitting around 455 nm. An absolute interferometer for length measurements in the range of several metres has been developed. Tuning this cavity length across a wavelength allows the laser to be tuned across a free spectral range c2 l around the grating gain peak where c, is the speed of light and l, is the cavity length, typically 1. We report a homebuilt external cavity diode laser ecdl, using a diode whose front facet is not antireflection ar coated, that has a modehopfree mhf tuning range greater than 140 ghz. An absolute distance interferometer with two external cavity.
A gratingtunable external cavity laser based on a semiconductor laser diode a thesis for the degree of master of science presented to dublin city university by brian kevin hurley b. The external cavity may also contain additional components such as. Compact tunable external cavity diode laser with diffraction. Coherent operation of an array of algaas diode lasers was obtained by placing the array in an external cavity which made use of the talbot self. Mode stability of external cavity diode lasers sebastian d. We achieved this by using a short external cavity and by simultaneously tuning the. A short extended cavity diode laser secdl is one in which the external feedback element is a partial re. A laser cavity built in this manner is often called an ecdl, extendedcavity diode laser, or externalcavity diode laser.
The use of frequencydependence reflection for the external cavity e. The national time service center of china is developing a compact, highly stable, 698 nm external cavity diode laser ecdl for dedicated use in a space strontium optical clock. A laser diode, ld, injection laser diode ild, or diode laser is a semiconductor device similar to a lightemitting diode in which a diode pumped directly with electrical current can create lasing conditions at the diode s junction 3 laser diodes can directly convert electrical energy into light. The practical and accessible information in this volume will enable the reader to study external cavity diode laser, to build up the systems of external cavity diode laser as well as to develop advanced systems for their particular applications. The frequency of a diode laser depends on the temperature of the laser and the current driving the laser. The basic idea is to use an extended cavity diode laser with the 1st order diffraction. External cavity diode laser with kilohertz linewidth by a monolithic folded fabryperot cavity optical feedback. The apparatus in this immersion will comprise components of a homebuilt external cavity diode laser system. The national time service center of china is developing a compact, highly stable, 698 nm externalcavity diode laser ecdl for dedicated use in a space strontium optical clock. This was also extended to operate an external cavity diode laser ecdl with no observed mode hops.
Mode stability of external cavity diode lasers wordpress at the. Due to the extreme sensitivity of laser frequency to cavity length 25mhznm for a 780nm diode, the grating mount, which is typically adjustable to allow for laser alignmentandtuning,shouldberigid. An externalcavity diode laser is a diode laser based on a laser diode chip which typically has one end antireflection coated, and the laser resonator is completed with, e. Stabilizing diode lasers to h ighfi n esse cavltl es. The pdh stabilization is accomplished via feedback to the laser diode current and the laser cavity piezo transducer pzt. They are used in optical communication and fiber sensor technology. Changing the length or refractive index of the cavity, for example by heating or cooling the laser diode, will shift the whole comb of modes and. The designed driver circuit was used to study the power and voltage variations versus current for a diode laser. Peter beyersdorf department of physics and astronomy dr. Construction and characterization of external cavity diode. To get high speed transmission, we use light but not just any light we use lasers. As noted above, the split cavity laser is relatively susceptible to external vibration.
Participants will have the opportunity to build, align and tune an ecdl at 633 nm and 780 nm. A typical 850 nm laser diode with a length of around 300 m and a group index around 4 will have a longitudinal mode spacing of 0. The laser source in this work is a diode laser in an external cavity ecdl in the littman configuration operating at 698 nm fig. Diodenlaser 405nm, sfaw210 mit externem resonator mit littrowaufbau.
The laser diode is a laser where the active medium is a semiconductor similar to that found in a lightemitting diode. Consequently, only when the threshold current is reached will the diode commence lasing. External cavity laser diodes ecls are lasers with a very small line width, very good wavelength stability, and very low noise. Developing an electronically controlled external cavity. These are small enough to endanger a diode laser life. External cavity laser diodes fibercoupled laser diodes. Pdf conventional raman technique requires a continuouswave laser with stabilized wavelength, narrow linewidth, and sufficient output power. We successfully apply it to explain the peculiar form of our. The most common type of laser diode is formed from a pn junction and powered by injected electric current. Recently, we have demonstrated large modehop free tuning of an externalcavity diode laser with an offtheshelf laser diode. Tuning range and output power optimization of an externalcavity. The obtained results can be used as a guide for selecting gratings for external cavity diode lasers for diferent requirements. The coupling efficiency for a single mode fibre exceeds 60%. External cavity diode lasers ecdls realworld atomic sensors and other exacting applications require laser sources with specific size, environmental, and optical characteristics, placing unique constraints that most commercial laser systems do not meet.
Littrow monolithic tunable external cavity laser, 370nm 1770nm, up to 300mw, patented technology, monolithic cavity design, handsoff operation, narrow linewidth, up to 30ghz modehop free tuning, free space and fiber coupled versions. Intracavity spectroscopy with diode lasers springerlink. We report a very compact external cavity diode laser system ecdl with an output power of up to 800mw with an almost gaussian shaped beam quality m 2 1. Pdf characterization of external cavity diode laser. Compact externalcavity diode laser with a novel transmission. Sc school of physical sciences dublin city university research supervisor. Tunable highpower externalcavity gan diode laser systems. We have developed externalcavity diode lasers, where the wavelength selection is assured by a low loss interference filter instead of the common diffraction. Pdf external cavity diode laser with kilohertz linewidth. Mode stability of external cavity diode lasers cdn.
Fang abstract in this report, a model of external cavity semiconductor laser is built, and then based on this model a program is coded for simulating the thermally induced wavelength shift and mode hopping. An external cavity diode laser is a diode laser based on a laser diode chip which typically has one end antireflection coated, and the laser resonator is completed with, e. A novel extendedcavity diode laser in red wavelengths. This is the first book on tunable external cavity semiconductor diode lasers, providing an uptodate survey on the physics, technology, and performance of. Check our arcoated diode stock list for availability.