Abstract

We present theory and simulations for a spectral narrowing scheme for laser diode arrays (LDAs) that employs optical feedback from a diffraction grating. We calculate the effect of the so-called smile of the LDA and show that it is possible to reduce the effect by using a cylindrical lens set at an angle to the beam. The scheme is implemented on a 19-element LDA with smile of 7.6 μm and yields frequency narrowing from a free-running width of 2 to 0.15 nm. The experimental results are in good agreement with the theory.

© 2005 Optical Society of America

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References

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  1. M. E. Wagshul, T. E. Chupp, “Optical pumping of high-density Rb with a broadband dye laser and GaAlAs diode laser arrays: application to 3He polarization,” Phys. Rev. A 40, 4447–4454 (1989).
    [CrossRef] [PubMed]
  2. A. L. Zook, B. B. Adhyaru, C. R. Bowers, “High capacity production of 65% spin polarized xenon-129 for NMR spectroscopy and imaging,” J. Magn. Resonance 159, 175–182 (2002).
    [CrossRef]
  3. B. Chann, I. Nelson, T. G. Walker, “Frequency-narrowed external cavity diode-laser-array bar,” Opt. Lett. 25, 1352–1354 (2000).
    [CrossRef]
  4. T. G. Walker, B. Chann, A. Nelson, “Frequency-narrowed high power diode laser array method and system,” U.S. Patent6,584,133:B1 (24June2003).
  5. N. U. Wetter, “Three-fold effective brightness increase of laser diode bar emission by assessment and correction of diode array curvature,” Opt. Laser Technol. 33, 181–187 (2001).
    [CrossRef]

2002 (1)

A. L. Zook, B. B. Adhyaru, C. R. Bowers, “High capacity production of 65% spin polarized xenon-129 for NMR spectroscopy and imaging,” J. Magn. Resonance 159, 175–182 (2002).
[CrossRef]

2001 (1)

N. U. Wetter, “Three-fold effective brightness increase of laser diode bar emission by assessment and correction of diode array curvature,” Opt. Laser Technol. 33, 181–187 (2001).
[CrossRef]

2000 (1)

1989 (1)

M. E. Wagshul, T. E. Chupp, “Optical pumping of high-density Rb with a broadband dye laser and GaAlAs diode laser arrays: application to 3He polarization,” Phys. Rev. A 40, 4447–4454 (1989).
[CrossRef] [PubMed]

Adhyaru, B. B.

A. L. Zook, B. B. Adhyaru, C. R. Bowers, “High capacity production of 65% spin polarized xenon-129 for NMR spectroscopy and imaging,” J. Magn. Resonance 159, 175–182 (2002).
[CrossRef]

Bowers, C. R.

A. L. Zook, B. B. Adhyaru, C. R. Bowers, “High capacity production of 65% spin polarized xenon-129 for NMR spectroscopy and imaging,” J. Magn. Resonance 159, 175–182 (2002).
[CrossRef]

Chann, B.

B. Chann, I. Nelson, T. G. Walker, “Frequency-narrowed external cavity diode-laser-array bar,” Opt. Lett. 25, 1352–1354 (2000).
[CrossRef]

T. G. Walker, B. Chann, A. Nelson, “Frequency-narrowed high power diode laser array method and system,” U.S. Patent6,584,133:B1 (24June2003).

Chupp, T. E.

M. E. Wagshul, T. E. Chupp, “Optical pumping of high-density Rb with a broadband dye laser and GaAlAs diode laser arrays: application to 3He polarization,” Phys. Rev. A 40, 4447–4454 (1989).
[CrossRef] [PubMed]

Nelson, A.

T. G. Walker, B. Chann, A. Nelson, “Frequency-narrowed high power diode laser array method and system,” U.S. Patent6,584,133:B1 (24June2003).

Nelson, I.

Wagshul, M. E.

M. E. Wagshul, T. E. Chupp, “Optical pumping of high-density Rb with a broadband dye laser and GaAlAs diode laser arrays: application to 3He polarization,” Phys. Rev. A 40, 4447–4454 (1989).
[CrossRef] [PubMed]

Walker, T. G.

B. Chann, I. Nelson, T. G. Walker, “Frequency-narrowed external cavity diode-laser-array bar,” Opt. Lett. 25, 1352–1354 (2000).
[CrossRef]

T. G. Walker, B. Chann, A. Nelson, “Frequency-narrowed high power diode laser array method and system,” U.S. Patent6,584,133:B1 (24June2003).

Wetter, N. U.

N. U. Wetter, “Three-fold effective brightness increase of laser diode bar emission by assessment and correction of diode array curvature,” Opt. Laser Technol. 33, 181–187 (2001).
[CrossRef]

Zook, A. L.

A. L. Zook, B. B. Adhyaru, C. R. Bowers, “High capacity production of 65% spin polarized xenon-129 for NMR spectroscopy and imaging,” J. Magn. Resonance 159, 175–182 (2002).
[CrossRef]

J. Magn. Resonance (1)

A. L. Zook, B. B. Adhyaru, C. R. Bowers, “High capacity production of 65% spin polarized xenon-129 for NMR spectroscopy and imaging,” J. Magn. Resonance 159, 175–182 (2002).
[CrossRef]

Opt. Laser Technol. (1)

N. U. Wetter, “Three-fold effective brightness increase of laser diode bar emission by assessment and correction of diode array curvature,” Opt. Laser Technol. 33, 181–187 (2001).
[CrossRef]

Opt. Lett. (1)

Phys. Rev. A (1)

M. E. Wagshul, T. E. Chupp, “Optical pumping of high-density Rb with a broadband dye laser and GaAlAs diode laser arrays: application to 3He polarization,” Phys. Rev. A 40, 4447–4454 (1989).
[CrossRef] [PubMed]

Other (1)

T. G. Walker, B. Chann, A. Nelson, “Frequency-narrowed high power diode laser array method and system,” U.S. Patent6,584,133:B1 (24June2003).

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Figures (5)

Fig. 1
Fig. 1

External cavity used for narrowing the diode array. The microlens collimates the beam in the plane perpendicular to the array (fast axis), and the telescope expands the beam in the plane of the array (slow axis) and images the elements onto the grating. The first lens of the telescope can be tilted about the axis shown. A screen can be placed instead of the grating to record images of the laser smile.

Fig. 2
Fig. 2

Image of the smile as the first cylindrical lens in the telescope arrangement is tilted. (a) Simulation of the effect of tilting the lens from −2° to 33°. (b) Actual image of the smile as the lens is tilted from −2° to 33°. Dashed boxes highlight the simulated and actual smile images with the lens untilted and with it tilted at the optimal angle of 23°.

Fig. 3
Fig. 3

Simulation of the laser linewidth, showing the measured positions, power, and linewidths of the individual elements. The lighter curves show the simulated line for each element, the darker solid curve represents the sum of all the individual elements, and the dashed curve represents the measured laser spectrum.

Fig. 4
Fig. 4

Diagram showing the path of a beam from a LDA element as it passes through the two surfaces of the lens (shaded). The incident beam is labeled a, and the refracted beam is labeled b. The planes that contain the incident, surface normal, and refracted rays are shown unshaded, with basis vectors v ^ 1 and v ^ 2 marked by heavy black lines. Any ray in this plane can be constructed from a linear combination of the two basis vectors.

Fig. 5
Fig. 5

Spectrum of the diode with narrowing. Dashed curve, the laser before tilting of the first cylindrical lens; solid curve, the laser after the lens has been tilted.

Equations (9)

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d λ λ = x cot θ M f f c ,
Δ x = f c Δ z y = 1.03 × 2.9 391 = 7.6 μ m ,
v ^ 1 = n ^ 1 = [ sin ( θ ) , 0 , cos ( θ ) ] ,
v 2 = a - n ^ 1 cos ( θ ) .
v ^ 2 = [ - cos ( θ ) , 0 , sin ( θ ) ] .
θ 2 = arcsin [ n 1 n 2 sin ( θ ) ] ,
b = cos ( θ 2 ) v ^ 1 + sin ( θ 2 ) v ^ 2 .
n ^ 2 = [ sin ( θ ) cos ( ϕ ) , sin ( ϕ ) , cos ( θ ) cos ( ϕ ) ] ,
ϕ = arcsin ( y / R ) .

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