Compare Model Drawings, CAD & Specs Diameter Effective Focal Length (EFL) F/# Availability Price
Plano-Concave Lens, N-BK7, 6.35 mm Diameter, -25 mm EFL, 650-1000 nm
$59
In Stock
6.35 mm -25 mm -3.9
In Stock
Plano-Concave Lens, N-BK7, 6.35 mm Diameter, -12.5 mm EFL, 650-1000 nm
$59
In Stock
6.35 mm -12.5 mm -1.9
In Stock
Plano-Concave Lens, N-BK7, 12.7 mm Diameter, -100 mm EFL, 650-1000 nm
$59
In Stock
12.7 mm -100 mm -7.8
In Stock
Plano-Concave Lens, N-BK7, 12.7 mm Diameter, -75 mm EFL, 650-1000 nm
$59
In Stock
12.7 mm -75 mm -5.9
In Stock
Plano-Concave Lens, N-BK7, 12.7 mm Diameter, -50 mm EFL, 650-1000 nm
$59
In Stock
12.7 mm -50 mm -3.9
In Stock
Plano-Concave Lens, N-BK7, 12.7 mm Diameter, -25 mm EFL, 650-1000 nm
$59
In Stock
12.7 mm -25 mm -1.9
In Stock
Plano-Concave Lens, N-BK7, 25.4 mm Diameter, -200 mm EFL, 650-1000 nm
$63
In Stock
25.4 mm -200 mm -7.8
In Stock
Plano-Concave Lens, N-BK7, 25.4 mm Diameter, -150 mm EFL, 650-1000 nm
$63
In Stock
25.4 mm -150 mm -5.9
In Stock
Plano-Concave Lens, N-BK7, 25.4 mm Diameter, -100 mm EFL, 650-1000 nm
$63
In Stock
25.4 mm -100 mm -3.9
In Stock
Plano-Concave Lens, N-BK7, 25.4 mm Diameter, -75 mm EFL, 650-1000 nm
$63
In Stock
25.4 mm -75 mm -2.9
In Stock
Plano-Concave Lens, N-BK7, 25.4 mm Diameter, -50 mm EFL, 650-1000 nm
$63
In Stock
25.4 mm -50 mm -1.9
In Stock
Plano-Concave Lens, N-BK7, 25.4 mm Diameter, -25 mm EFL, 650-1000 nm
$63
In Stock
25.4 mm -25 mm -0.9
In Stock
Plano-Concave Lens, N-BK7, 50.8 mm Diameter, -500 mm EFL, 650-1000 nm
$99
In Stock
50.8 mm -500 mm -9.8
In Stock
Plano-Concave Lens, N-BK7, 50.8 mm Diameter, -250 mm EFL, 650-1000 nm
$99
In Stock
50.8 mm -250 mm -4.9
In Stock
Plano-Concave Lens, N-BK7, 50.8 mm Diameter, -200 mm EFL, 650-1000 nm
$99
In Stock
50.8 mm -200 mm -3.9
In Stock
Plano-Concave Lens, N-BK7, 50.8 mm Diameter, -150 mm EFL, 650-1000 nm
$99
In Stock
50.8 mm -150 mm -2.9
In Stock
Plano-Concave Lens, N-BK7, 50.8 mm Diameter, -100 mm EFL, 650-1000 nm
$99
In Stock
50.8 mm -100 mm -1.9
In Stock
Plano-Concave Lens, N-BK7, 50.8 mm Diameter, -75 mm EFL, 650-1000 nm
$99
In Stock
50.8 mm -75 mm -1.4
In Stock

Specifications

  • Lens Shape
    Plano-Concave
  • Lens Material
    N-BK7
  • Antireflection Coating
    650-1000 nm
  • Coating Type
    NIR Multilayer
  • Coating Code
    AR.16
  • Damage Threshold
    7.5 J/cm2, 10 ns pulses, 10 Hz at 1064 nm
  • Surface Quality
    40-20 scratch-dig
  • Surface Accuracy, Irregularity
    λ/4
  • Surface Accuracy, Power
    1.5 λ
  • Surface Flatness
    λ/4
  • Centration
    ≤3 arc min
  • Chamfers
    0–0.8 mm face width
  • Chamfers Angle/Tolerance
    45° ±15°, typical
  • Focal Length Tolerance
    ±1 %
  • Diameter Tolerance
    +0/-0.1 mm
  • Clear Aperture
    ≥central 90% of diameter
  • Cleaning

Features

N-BK7 Substrates for VIS and NIR Applications

N-BK7 is an excellent lens material for most visible and near infrared applications. It is the most common borosilicate crown optical glass, and it provides great performance at a good value. Its high homogeneity, low bubble and inclusion content, and straightforward manufacturability make it a good choice for transmissive optics. N-BK7 is also relatively hard and shows good scratch resistance. The transmission range for BK 7 is 380 to 2100 nm. It is not recommended for temperature sensitive applications, such as precision mirrors. For more information, refer to our optical materials technical note.

High Quality Precision Plano-Concave Lens Surfaces

Our precision plano-concave lenses are polished to tight tolerances minimizing wavefront distortion. Tight surface quality tolerances minimize scatter and unwanted diffraction effects. These lenses have a 40-20 scratch-dig surface quality, and a 1.5 λ surface power accuracy. For more information, refer to the optical surfaces technical note.

Broadband Multilayer NIR Antireflection Coatings

Our broadband AR.16 antireflection coating improves the transmission efficiency of these lenses by reducing surface reflections over a 650-1000 nm wavelength range. The NIR AR multi-layer coating improves the performance over uncoated surfaces. It features a damage threshold of 7.5 J/cm‌2 for 10 ns pulses at 10 Hz and 1064 nm.

Standardized Plano-Concave Focal Lengths

Standard effective focal lengths on our plano-concave lenses provide a systematic approach allowing for lenses of different sizes and materials to be interchanged without requiring other changes to your optical system.

Mounted Version - with Lens Tubes

The lenses can be mounted in LT series lens tube for constructing a complex optical system or quickly connecting to other threaded lens mounts: A-Line™ series fixed lens mount, or adjustable lens positioner (with thread adapter). Use LT-WR series spanner wrench for easy lens installation.

Expanding a Laser Beam with a Plano-Concave Lens

As an application example, consider a Newport R-31005 HeNe Laser with beam diameter 0.63 mm and a divergence of 1.3 mrad. Note that these are beam diameter and full divergence, so in the notation of our figure, y1 = 0.315 mm and θ1= 0.65 mrad. To expand this beam ten times while reducing the divergence by a factor of ten, we could select a plano-concave lens KPC043 with f1 = -25 mm and a plano-convex lens KPX109 with f2 = 250 mm. Since real lenses differ in some degree from thin lenses, the spacing between the pair of lenses is actually the sum of the back focal lengths BFL1 + BFL2 = -26.64 mm + 247.61 mm = 220.97 mm.

The expanded beam diameter is: 2y3 = 2y1f2/|-f1| = 2(0.315 mm)(250 mm)/|-25 mm|= 6.3 mm. 

The divergence angle is: θ3 = θ1|-f1|/f2 = (0.65 mrad)|-25 mm|/250 mm = 0.065 mrad.

For minimal aberrations, it is best to use a plano-concave lens for the negative lens and a plano-convex lens for the positive lens with the plano surfaces facing each other. To further reduce aberrations, only the central portion of the lens should be illuminated, so choosing oversized lenses is often a good idea. This style of beam expander is called Galilean.

Mounting Options

We offer a full range of optical lens mounts to meet various experimental requirements. Below lists the recommended mounts for spherical lenses of standard sizes. Please see our Lens Mount Guide for additional information.

Lens Diameter LH-A-GRP
A-Line™ Lens Mounts
LT_Series_group_update
LT Series Lens Tubes
OM-multi_axis_lens_pos-S
LP Series Lens Positioners
optics-cage-plus-S
Optics Cage Plus Series
76.2 mm (M-) LH-3A N/A N/A N/A
50.8 mm (M-) LH-2A
LH-2N
LT20-05
LT20-10
LT20-20
LT20-30
LP-2A
LP-2A-XY
LP-2A-XYZ
N/A
38.1 mm (M-) LH-1.5A LT20 lens tube with
LH-2R1.5 adapter
LP-2 lens positioner with
LPLH-1.5T adapter
N/A
25.4 mm (M-) LH-1A
LH-1N
LH-1XY
LH-1TZ-A
LH-1TZ
LT10-05
LT10-10
LT10-20
LT10-30
LP-1A
LP-1A-XY
LP-1A-XYZ
OC1-LH1-S
OC1-LH1
OC1-LH1-TZ
OC1-LH1-XY
OC1-LH1-XYA
OC1-LH1-XYC
OC1-LH1-XYZ
12.7 mm (M-) LH-0.5A
LH-05N
LT05-05
LT05-10
LP-05A
LP-05A-XY
LP-05A-XYZ
N/A
6.35 mm LH-05DB with
LH-50R25 adapter
LT05 lens tube with
LH-50R25 adapter
LP-05 lens positioner with
LPLH-25T adapter
N/A

For non-standard sizes not listed above, check out our variable size lens mounts.