Volume Holographic Grating Wavelength Stabilized Laser Diodes

Steckman, Gregory J.; Liu, Wenhai; Platz, R.; Schroeder, Daniel J.; Moser, Christophe; Havermeyer, Frank

doi:10.1109/jstqe.2007.896060

Cited by 65 publications

(30 citation statements)

References 19 publications

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“…The two most common approaches utilized in the high power diode laser arena are internal buried distributed Bragg gratings (DFBs) [4] and external volumetric Bragg gratings (also commonly referred to as VHGs for volume holographic grating) [5][6]. VHGs are external optical components in which a periodic variation in index of refraction has been written into the photorefractive glass, which thereby provides wavelength-(and angular-) selective feedback.…”

Section: Vhg Locked Diode Lasersmentioning

confidence: 99%

High-performance wavelength-locked diode lasers

et al. 2009

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Rapidly maturing industrial laser applications are placing ever-tighter constraints on spectral width and wavelength emission stability over varying operating temperatures of high power diode laser pump sources. For example, improved power scaling and efficiency can be achieved by pumping the narrow upper laser level of Nd:YAG solid state lasers at 885 nm and the 1532-nm absorption band of Er:YAG solid state lasers, though taking full advantage of these configurations requires wavelength-locked pump sources. nLight offers a wide variety of wavelength-locked diode products based on external volume grating optics technology. It is often believed that the use of external gratings to wavelength lock diode lasers leads to an unavoidable loss in power and efficiency. nLight's design methodology is shown to eliminate the problem in our grating-locked diode laser products. These results are expected to enable improved performance in diode-pumped solid state and fiber laser systems. MOTIVATIONRapidly maturing industrial laser applications are placing ever-tighter constraints on spectral width and wavelengthtemperature control of high power diode laser pump sources. For example, improved power scaling and efficiency can be achieved by pumping the narrow upper laser level of Nd:YAG solid state lasers at 885 nm and the 1532-nm absorption band of Er:YAG solid state lasers, though taking full advantage of these configurations requires diode pump sources with narrowed spectral lines [1,2]. Figure 1 illustrates the absorption spectra of Nd:YAG and Er:YAG at these wavelengths. As shown, the absorption feature at 885 nm in Nd:YAG is < 2.5 nm FWHM and at 1532 nm in Er:YAG is < 1 nm FWHM. The typical unlocked 885-nm broad area diode laser spectral width is ~2.5 nm, with the peak wavelength shifting at ~0.25 nm/°C; at 1532-nm the spectral width of the diode increases to ~6 nm with the peak shifting at ~0.4 nm/°C. Efficient laser systems requiring uniform absorption of the pump light require the diode source be wellmatched (in terms of spectral width and spectral position) to the absorption feature. The drift of operating wavelength with temperature of conventional diode lasers also sets strict requirements on thermal control of the diode pump source. 875 880 885 890 895 Wavelength (nm) Absorption (arb. units) 0 0.5 1 1.5 2 2.5 3 3.5 4 1524 1528 1532 1536 1540 Absorption (arb. units) Wavelength (nm) 0.72nm FWHM Nd:YAG Er:YAG Fig. 1: The absorption spectra of (left) Nd:YAG around 885-nm [1] and (right) Er:YAG around 1532nm [2]. *paul.leisher@nlight.net; phone 360.713.5230; http://www.nlight.net Sponsorship by the High Energy Laser Joint Technology Office (HEL-JTO), Albuquerque, NM is acknowledged

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Section: Vhg Locked Diode Lasersmentioning

confidence: 99%

High-performance wavelength-locked diode lasers

et al. 2009

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“…Furthermore, it is expected that the emission bandwidth could be further reduced to the sub-MHz level (in accordance with the Schawlow-Townes time-averaged linewidth equation) due to a long passive cavity length [8]. Volume holographic gratings (VHGs) have been successfully used to wavelength lock semiconductor lasers [9]. In this work, a VHG is used to stabilize the emission wavelength of an optically-pumped 780 nm VECSEL.…”

mentioning

confidence: 93%

Volume holographic grating stabilized 780nm VECSEL

2014

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We report on an optically pumped vertical-external-cavity surface-emitting laser diode coupled by a high reflectance volume holographic grating (VHG). The major feature of such a system is very narrow linewidth and high degree of power scalability, required for pumping upper energy levels of a gain medium. The cavity design lends itself to scaling to 2D VECSEL arrays suitable for low cost, high brightness pump sources.Keywords: VECSEL, high brightness, high power MOTIVATIONVertical External Cavity Surface Emitting Lasers (VECSELs), also called semiconductor disk lasers, are showing promise as next-generation sources for communications, laser cooling, spectroscopy, and high power direct use. Surface-emitting lasers have several advantages over bar-type diodes, namely a significant improvement in beam quality at high powers due to low-order mode operation [1,2]. This class of laser, however, suffers from relatively broad emission linewidth. For applications such as fiber optic communications, diode pumping, and atomic physics, some method of wavelength locking is typically required [3][4][5]. For example, in pumping applications, materials with narrow gain bandwidths (common in low quantum-defect lasers) require that the diode pump source be spectrally matched to the absorption feature to ensure efficiency pumping. Due to an external output coupler, VECSELs have greater adjustability and a greater possible number of cavity designs than other semiconductor lasers [6]. This allows for larger mode sizes and simple 2D scaling, leading to higher output powers in low-order modes than are possible with other laser types, as well the ability to easily incorporate wavelength-selective feedback to accurately control and lock the laser emission [7]. Furthermore, it is expected that the emission bandwidth could be further reduced to the sub-MHz level (in accordance with the Schawlow-Townes time-averaged linewidth equation) due to a long passive cavity length [8]. Volume holographic gratings (VHGs) have been successfully used to wavelength lock semiconductor lasers [9]. In this work, a VHG is used to stabilize the emission wavelength of an optically-pumped 780 nm VECSEL. EXPERIMENTThe design of the VECSEL epitaxy, as shown in Fig. 1 (a), is based partially on the designs reported in [10] and [11], and consists of a highly reflective bottom DBR and partially reflective top DBR surrounding a multi-quantum well active region. The Design provides high operating efficiency of the quantum wells and helps account for thermal effects within the structure. To maintain low optical loss, none of the layers were intentionally doped. The structure was grown bottom-up with the pump reflector DBR built directly onto the GaAs substrate wafer. A sample of the wafer was thinned and cleaved to a square sample for testing. The chip was mounted directly to a Cu heatsink (substrate side down) for testing.

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“…In broad-area laser diodes, two such techniques are employing a distributed Bragg reflector on the diode [3,4] or a volume Bragg reflector in an external cavity configuration [5][6][7]. While a distributed Bragg reflector is monolithically integrated on the diode and does not require physical alignment, such devices still suffer from wavelength variability due to temperature and, therefore, operating power.…”

Section: Introductionmentioning

confidence: 99%

Spectral Narrowing and Stabilization for Broad-Area Lasers via Modified Delivery Fiber

Leidner

Marciante

2015

IEEE Photon. Technol. Lett.

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A proof-of-concept experiment for fiber-based broad-area laser stabilization is experimentally demonstrated using coupling optics and a 1-nm wide, 98% reflectivity fiber Bragg grating. The output spectrum of a 3 W, 100 micron wide, 2 mm long commercial broad-area laser was narrowed by more than 10x to 0.26 nm full-width half-max. Additionally, the system showed 7-13% enhanced output power. The system also shows potential for slow-axis beam quality improvement in the desired operating regime. A pump delivery fiber scheme is proposed for integration of the diode feedback into a pump system package for enhanced-brightness fiber pumping.

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Volume Holographic Grating Wavelength Stabilized Laser Diodes

Cited by 65 publications

References 19 publications

High-performance wavelength-locked diode lasers

High-performance wavelength-locked diode lasers

Volume holographic grating stabilized 780nm VECSEL

Spectral Narrowing and Stabilization for Broad-Area Lasers via Modified Delivery Fiber

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