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N-BK7 Unmounted Spherical Singlet Lens Kits


  • Single Solution for Storing and Stocking Optics
  • AR-Coated Spherical Singlets
  • Kits Containing Ø1" Lenses or Various Diameters

ESK52-B

ESK53-B

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Spherical Singlet Lens Kit Selection Guide
Mounted N-BK7
Unmounted N-BK7
Mounted UV Fused Silica
Mounted Calcium Fluoride (CaF2)
Damage Thresholds
-A Coating 7.5 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.504 mm)
-B Coating 7.5 J/cm2 (810 nm, 10 ns, 10 Hz, Ø0.144 mm)

Features

  • Unmounted N-BK7 Spherical Singlets Packaged into Kits
  • Kits Contain Lenses that are Ø1" or an Array of Sizes
  • Available with One of Two AR Coatings
    • -A (350 - 700 nm)
    • -B (650 - 1050 nm)
  • Laser Quality: 40-20 (Scratch-Dig)
  • Offered at a Savings Over Purchasing the Lenses Individually
  • Heavy-Duty Welded Steel Cabinet Frame

Thorlabs offers two types of kits that house our most popular unmounted N-BK7 spherical singlets, both of which are available with either our -A (350 - 700 nm) or -B (650 - 1050 nm) broadband antireflection coating. ESK52-A and ESK52-B each contain 101 of our most popular plano-convex and bi-convex lenses in various sizes while ESK53-A and ESK53-B each contain 60 of our most popular Ø1" spherical singlets.

These lenses are fabricated from RoHS-compliant BK7 glass (N-BK7). N-BK7 is probably the most common optical glass used for high quality optical components. It is typically chosen whenever the additional benefits of UV fused silica (i.e., good transmission further into the UV and a lower coefficient of thermal expansion) are not necessary.

Lens TypeFunction
Plano Convex Plano-Convex lenses have a positive focal length and near-best-form shape for infinite and finite conjugate applications. They can be employed to converge collimated beams or collimate light from a point source. To minimize the introduction of spherical aberration, a collimated light source should be incident on the curved surface of the lens when being focused and a point light source should be incident on the planar surface when being collimated. They are best used where one conjugate point (object distance S or image distance S') is more than five times the other.
Bi Convex Bi-Convex lenses have a positive focal length and are most suitable for use when the object and image are on opposite sides of the lens and the ratio of the object-to-image distance (conjugate ratio) is between 0.2 and 5.0.
Plano Concave Plano-Concave lenses have a negative focal length and are typically used to cause a collimated beam to diverge as in a Galilean-type beam expander or telescope. Since the spherical aberration of the plano-concave lens is negative, it can be used to balance the aberration of the other lenses.
Bi Concave Like plano-concave lenses, bi-concave lenses have negative focal lengths and can be used to increase the divergence of a beam of light. They are best suited for situations where the incident beam of light is converging.
Positive Meniscus Positive meniscus lenses are designed to minimize spherical aberration. One surface of the lens is convex, while the other surface is concave. When used in combination with another lens, a positive meniscus lens will shorten the focal length, and increase the NA of the system. These lenses are commonly used to achieve tighter beam focusing when paired with another positive lens.
Negative Meniscus Negative meniscus (convex-concave) lenses, which are thinner in the middle than at the edges and cause light rays to diverge, are designed to minimize third-order spherical aberration. They are often used in conjunction with other lenses to increase the focal length, and therefore decrease the numerical aperture (NA), of an optical assembly.

The following tables display all of the lenses included with the lens kits sold on this page. Click "More" to see the full list of lenses included with each kit. Once expanded, each lens item number in the table can be clicked to view our standard support documents, more product information, and individual purchasing options.

Contents of ESK53 Ø1" Spherical Singlet Lens Kits

ESK53-A Ø1" Spherical Singlet Lens Kit (ARC: 350 - 700 nm)
ESK53-B Ø1" Spherical Singlet Lens Kit (ARC: 650 - 1050 nm)
  • Reciprocal of Focal Length in Meters
  • This lens is only available as part of a kit. Please contact tech support to purchase this lens individually.

Contents of ESK52 Spherical Singlet Lens Kits with Various Diameters

ESK52-A Spherical Singlet Lens Kit with Various Optic Diameters (ARC: 50 - 700 nm)
ESK52-B Spherical Singlet Lens Kit with Various Optic Diameters (ARC: 650 - 1050 nm)
  • Reciprocal of Focal Length in Meters
  • This lens is only available as part of a kit. Please contact tech support to purchase this lens individually.
A AR Coating
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Click Here for Raw Data
The blue shaded region indicates the specified 350 - 700 nm wavelength range for optimum performance.
B AR Coating
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Click Here for Raw Data
The blue shaded region indicates the specified 650 - 1050 nm wavelength range for optimum performance.

Thorlabs' Standard Broadband Antireflection Coatings

Damage Threshold Specifications
Coating Designation
(Item # Suffix)
Damage Threshold
-A 7.5 J/cm2 (532 nm, 10 ns, 10 Hz, Ø0.504 mm)
-B 7.5 J/cm2 (810 nm, 10 ns, 10 Hz, Ø0.144 mm)

Damage Threshold Data for Thorlabs' NBK-7 Singlet Lenses

The specifications to the right are measured data for Thorlabs' NBK-7 spherical singlet lenses. Damage threshold specifications are constant for a given coating type, regardless of the size or shape of the lens.

 

Laser Induced Damage Threshold Tutorial

The following is a general overview of how laser induced damage thresholds are measured and how the values may be utilized in determining the appropriateness of an optic for a given application. When choosing optics, it is important to understand the Laser Induced Damage Threshold (LIDT) of the optics being used. The LIDT for an optic greatly depends on the type of laser you are using. Continuous wave (CW) lasers typically cause damage from thermal effects (absorption either in the coating or in the substrate). Pulsed lasers, on the other hand, often strip electrons from the lattice structure of an optic before causing thermal damage. Note that the guideline presented here assumes room temperature operation and optics in new condition (i.e., within scratch-dig spec, surface free of contamination, etc.). Because dust or other particles on the surface of an optic can cause damage at lower thresholds, we recommend keeping surfaces clean and free of debris. For more information on cleaning optics, please see our Optics Cleaning tutorial.

Testing Method

Thorlabs' LIDT testing is done in compliance with ISO/DIS 11254 and ISO 21254 specifications.

First, a low-power/energy beam is directed to the optic under test. The optic is exposed in 10 locations to this laser beam for 30 seconds (CW) or for a number of pulses (pulse repetition frequency specified). After exposure, the optic is examined by a microscope (~100X magnification) for any visible damage. The number of locations that are damaged at a particular power/energy level is recorded. Next, the power/energy is either increased or decreased and the optic is exposed at 10 new locations. This process is repeated until damage is observed. The damage threshold is then assigned to be the highest power/energy that the optic can withstand without causing damage. A histogram such as that below represents the testing of one BB1-E02 mirror.

LIDT metallic mirror
The photograph above is a protected aluminum-coated mirror after LIDT testing. In this particular test, it handled 0.43 J/cm2 (1064 nm, 10 ns pulse, 10 Hz, Ø1.000 mm) before damage.
LIDT BB1-E02
Example Test Data
Fluence # of Tested Locations Locations with Damage Locations Without Damage
1.50 J/cm2 10 0 10
1.75 J/cm2 10 0 10
2.00 J/cm2 10 0 10
2.25 J/cm2 10 1 9
3.00 J/cm2 10 1 9
5.00 J/cm2 10 9 1

According to the test, the damage threshold of the mirror was 2.00 J/cm2 (532 nm, 10 ns pulse, 10 Hz, Ø0.803 mm). Please keep in mind that these tests are performed on clean optics, as dirt and contamination can significantly lower the damage threshold of a component. While the test results are only representative of one coating run, Thorlabs specifies damage threshold values that account for coating variances.

Continuous Wave and Long-Pulse Lasers

When an optic is damaged by a continuous wave (CW) laser, it is usually due to the melting of the surface as a result of absorbing the laser's energy or damage to the optical coating (antireflection) [1]. Pulsed lasers with pulse lengths longer than 1 µs can be treated as CW lasers for LIDT discussions.

When pulse lengths are between 1 ns and 1 µs, laser-induced damage can occur either because of absorption or a dielectric breakdown (therefore, a user must check both CW and pulsed LIDT). Absorption is either due to an intrinsic property of the optic or due to surface irregularities; thus LIDT values are only valid for optics meeting or exceeding the surface quality specifications given by a manufacturer. While many optics can handle high power CW lasers, cemented (e.g., achromatic doublets) or highly absorptive (e.g., ND filters) optics tend to have lower CW damage thresholds. These lower thresholds are due to absorption or scattering in the cement or metal coating.

Linear Power Density Scaling

LIDT in linear power density vs. pulse length and spot size. For long pulses to CW, linear power density becomes a constant with spot size. This graph was obtained from [1].

Intensity Distribution

Pulsed lasers with high pulse repetition frequencies (PRF) may behave similarly to CW beams. Unfortunately, this is highly dependent on factors such as absorption and thermal diffusivity, so there is no reliable method for determining when a high PRF laser will damage an optic due to thermal effects. For beams with a high PRF both the average and peak powers must be compared to the equivalent CW power. Additionally, for highly transparent materials, there is little to no drop in the LIDT with increasing PRF.

In order to use the specified CW damage threshold of an optic, it is necessary to know the following:

  1. Wavelength of your laser
  2. Beam diameter of your beam (1/e2)
  3. Approximate intensity profile of your beam (e.g., Gaussian)
  4. Linear power density of your beam (total power divided by 1/e2 beam diameter)

Thorlabs expresses LIDT for CW lasers as a linear power density measured in W/cm. In this regime, the LIDT given as a linear power density can be applied to any beam diameter; one does not need to compute an adjusted LIDT to adjust for changes in spot size, as demonstrated by the graph to the right. Average linear power density can be calculated using the equation below. 

The calculation above assumes a uniform beam intensity profile. You must now consider hotspots in the beam or other non-uniform intensity profiles and roughly calculate a maximum power density. For reference, a Gaussian beam typically has a maximum power density that is twice that of the uniform beam (see lower right).

Now compare the maximum power density to that which is specified as the LIDT for the optic. If the optic was tested at a wavelength other than your operating wavelength, the damage threshold must be scaled appropriately. A good rule of thumb is that the damage threshold has a linear relationship with wavelength such that as you move to shorter wavelengths, the damage threshold decreases (i.e., a LIDT of 10 W/cm at 1310 nm scales to 5 W/cm at 655 nm):

CW Wavelength Scaling

While this rule of thumb provides a general trend, it is not a quantitative analysis of LIDT vs wavelength. In CW applications, for instance, damage scales more strongly with absorption in the coating and substrate, which does not necessarily scale well with wavelength. While the above procedure provides a good rule of thumb for LIDT values, please contact Tech Support if your wavelength is different from the specified LIDT wavelength. If your power density is less than the adjusted LIDT of the optic, then the optic should work for your application. 

Please note that we have a buffer built in between the specified damage thresholds online and the tests which we have done, which accommodates variation between batches. Upon request, we can provide individual test information and a testing certificate. The damage analysis will be carried out on a similar optic (customer's optic will not be damaged). Testing may result in additional costs or lead times. Contact Tech Support for more information.

Pulsed Lasers

As previously stated, pulsed lasers typically induce a different type of damage to the optic than CW lasers. Pulsed lasers often do not heat the optic enough to damage it; instead, pulsed lasers produce strong electric fields capable of inducing dielectric breakdown in the material. Unfortunately, it can be very difficult to compare the LIDT specification of an optic to your laser. There are multiple regimes in which a pulsed laser can damage an optic and this is based on the laser's pulse length. The highlighted columns in the table below outline the relevant pulse lengths for our specified LIDT values.

Pulses shorter than 10-9 s cannot be compared to our specified LIDT values with much reliability. In this ultra-short-pulse regime various mechanics, such as multiphoton-avalanche ionization, take over as the predominate damage mechanism [2]. In contrast, pulses between 10-7 s and 10-4 s may cause damage to an optic either because of dielectric breakdown or thermal effects. This means that both CW and pulsed damage thresholds must be compared to the laser beam to determine whether the optic is suitable for your application.

Pulse Duration t < 10-9 s 10-9 < t < 10-7 s 10-7 < t < 10-4 s t > 10-4 s
Damage Mechanism Avalanche Ionization Dielectric Breakdown Dielectric Breakdown or Thermal Thermal
Relevant Damage Specification No Comparison (See Above) Pulsed Pulsed and CW CW

When comparing an LIDT specified for a pulsed laser to your laser, it is essential to know the following:

Energy Density Scaling

LIDT in energy density vs. pulse length and spot size. For short pulses, energy density becomes a constant with spot size. This graph was obtained from [1].

  1. Wavelength of your laser
  2. Energy density of your beam (total energy divided by 1/e2 area)
  3. Pulse length of your laser
  4. Pulse repetition frequency (prf) of your laser
  5. Beam diameter of your laser (1/e2 )
  6. Approximate intensity profile of your beam (e.g., Gaussian)

The energy density of your beam should be calculated in terms of J/cm2. The graph to the right shows why expressing the LIDT as an energy density provides the best metric for short pulse sources. In this regime, the LIDT given as an energy density can be applied to any beam diameter; one does not need to compute an adjusted LIDT to adjust for changes in spot size. This calculation assumes a uniform beam intensity profile. You must now adjust this energy density to account for hotspots or other nonuniform intensity profiles and roughly calculate a maximum energy density. For reference a Gaussian beam typically has a maximum energy density that is twice that of the 1/e2 beam.

Now compare the maximum energy density to that which is specified as the LIDT for the optic. If the optic was tested at a wavelength other than your operating wavelength, the damage threshold must be scaled appropriately [3]. A good rule of thumb is that the damage threshold has an inverse square root relationship with wavelength such that as you move to shorter wavelengths, the damage threshold decreases (i.e., a LIDT of 1 J/cm2 at 1064 nm scales to 0.7 J/cm2 at 532 nm):

Pulse Wavelength Scaling

You now have a wavelength-adjusted energy density, which you will use in the following step.

Beam diameter is also important to know when comparing damage thresholds. While the LIDT, when expressed in units of J/cm², scales independently of spot size; large beam sizes are more likely to illuminate a larger number of defects which can lead to greater variances in the LIDT [4]. For data presented here, a <1 mm beam size was used to measure the LIDT. For beams sizes greater than 5 mm, the LIDT (J/cm2) will not scale independently of beam diameter due to the larger size beam exposing more defects.

The pulse length must now be compensated for. The longer the pulse duration, the more energy the optic can handle. For pulse widths between 1 - 100 ns, an approximation is as follows:

Pulse Length Scaling

Use this formula to calculate the Adjusted LIDT for an optic based on your pulse length. If your maximum energy density is less than this adjusted LIDT maximum energy density, then the optic should be suitable for your application. Keep in mind that this calculation is only used for pulses between 10-9 s and 10-7 s. For pulses between 10-7 s and 10-4 s, the CW LIDT must also be checked before deeming the optic appropriate for your application.

Please note that we have a buffer built in between the specified damage thresholds online and the tests which we have done, which accommodates variation between batches. Upon request, we can provide individual test information and a testing certificate. Contact Tech Support for more information.


[1] R. M. Wood, Optics and Laser Tech. 29, 517 (1998).
[2] Roger M. Wood, Laser-Induced Damage of Optical Materials (Institute of Physics Publishing, Philadelphia, PA, 2003).
[3] C. W. Carr et al., Phys. Rev. Lett. 91, 127402 (2003).
[4] N. Bloembergen, Appl. Opt. 12, 661 (1973).

ESK52-A SmartPack Packaging
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ESK52-A Packaging

Smart Pack

Item #% Weight
Reduction
CO2-Equivalent
Reductiona
ESK52-A 83.10% 20.80 kg
ESK52-B 83.10% 4.46 kg
ESK53-A 83.10% 40.12 kg
ESK53-B 83.10% 26.75 kg

Smart Pack

  • Reduce Weight of Packaging Materials
  • Increase Usage of Recyclable Packing Materials
  • Improve Packing Integrity
  • Decrease Shipping Costs

Thorlabs' Smart Pack Initiative is aimed at waste minimization while still maintaining adequate protection for our products. By eliminating any unnecessary packaging, implementing packaging design changes, and utilizing eco-friendly packaging materials for our customers when possible, this initiative seeks to improve the environmental impact of our product packaging. Products listed above are now shipped in re-engineered packaging that minimizes the weight and the use of non-recyclable materials.b As we move through our product line, we will indicate re-engineered packages with our Smart Pack logo.

  • Travel-based emissions reduction calculations are estimated based on the total weight reduction of packaging materials used for all of 2013’s product sales, traveling 1,000 miles on an airplane, to provide general understanding of the impact of packaging material reduction. Calculations were made using the EPA’s shipping emissions values for different modes of transport.
  • Some Smart Pack products may show a negative weight reduction percentage as the substitution of greener packaging materials, such as the Greenwrap, at times slightly increases the weight of the product packaging.

Posted Comments:
Ali Kemal Kazar  (posted 2019-11-14 13:21:04.963)
Hi, I would like to implement a Lens to our radar sensor (@77 GHz). By this way, the antenna performance of the system is going to be increased. Do you have lenses for this frequency band (75-85 GHz)? Do you have any application note and mounting procedure how to integrate your lenses to our radar sensor? Is it possible to calculate performance improvement of an patch antenna with a lens? Antenna beam-width is an important parameter for us, we would like to understand the effect of lens on beam-width of antenna. Looking forward to hearing from you. Regards Ali Kemal Kazar
YLohia  (posted 2019-11-14 12:07:43.0)
Hello Ali, thank you for contacting Thorlabs. Unfortunately, we currently do not offer lenses for the 77 GHz regime. Our current offerings of PTFE lenses (https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=1627) are designed for >500 GHz ranges.

Unmounted Ø1" AR-Coated Spherical Singlets Lens Kits

  • Kit Contains 60 Spherical Singlet Lenses
  • Positive Focal Lengths from 25.4 - 1000 mm
  • Negative Focal Lengths from -50 to -1000 mm
  • AR Coatings for 350 - 700 nm or 650 - 1050 nm

The ESK53-A and ESK53-B are AR-coated lens sets containing 18 plano-convex lenses (LA Series), 18 bi-convex lenses (LB Series), 3 plano-concave lenses (LC Series), 3 bi-concave lenses (LD Series), 9 positive meniscus lenses (LE Series), and 9 negative meniscus lenses (LF Series). Click on the Kit Contents tab above to see a list of the exact lenses included in this kit.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
ESK53-A Support Documentation
ESK53-AØ1" N-BK7 Plano-/Bi- Convex/Concave +/- Meniscus Lens Essentials Kit, ARC: 350-700 nm, 60 pc
$1,803.89
Today
ESK53-B Support Documentation
ESK53-BØ1" N-BK7 Plano-/Bi-Convex/Concave +/- Meniscus Lens Essentials Kit, ARC: 650-1050 nm, 60 pc
$1,803.89
Today

Unmounted AR-Coated Plano-Convex and Bi-Convex Lens Kits

  • Kit Includes 57 Plano-Convex and 44 Bi-Convex Lenses
  • Diameters Range from 6 - 75 mm
  • Focal Lengths from 10 - 1000 mm
  • AR Coatings for 350 - 700 nm or 650 - 1050 nm

The ESK52-A and ESK52-B are lens sets containing 57 AR-coated plano-convex lenses (LA Series) and 44 AR-coated bi-convex lenses (LB Series). Click on the Kit Contents tab above to see a list of the exact lenses included in this kit.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
ESK52-A Support Documentation
ESK52-AVarious Diameters, N-BK7 Plano-/Bi-Convex Lens Essentials Kit, ARC: 350-700 nm, 101 pc
$3,540.69
Today
ESK52-B Support Documentation
ESK52-BVarious Diameters N-BK7 Plano-/Bi-Convex Lens Essentials Kit, ARC: 650-1050 nm, 101 pc
$3,540.69
Today
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