Measuring instrument

Laser Focal Profiler (LFP)


  • Overview
  • Principle
  • Specifications
  • Operation
  • Original paper


Laser focal profiler (LFP) is a precise measuring instrument for the intensity distribution near the laser focal spot. LFP is the world's first instrument and unique product to make it possible to measure the ultra-fine focal spot formed by high NA (numerical aperture) lens.

The intensity distribution near the laser focal spot is a key performance indicator of many laser micro-/nanotechnologies. It evaluates the spatial resolution of laser microscopes, the efficiency of laser beam machining, the record density of optical data storage, the spring constant of force measurement systems with optical trapping, performance of microscope objective lenses.

A beam profiler using a CCD/CMOS camera as a commercial product is available for intensity profiling of the cross-section of the propagating laser Beam. However, it is difficult to apply directly for the laser focal spot with an microscope objective lens due to the limited spatial resolution originated to a large pixel size, which is more than a micron at minimum. To apply this profiler to a focal spot smaller than the pixel size, the focal spot needs to be magnified with optics and imaged onto the detector. However, this magnification method may induce unwanted aberrations; it is difficult to align and requires that the magnification optics have a higher 𝑁𝐴 than those used for focusing the laser beam.

The knife-edge method is another in situ technique that has been suggested but is not commercialized for a small laser focal spot because of several reasons as sharpness of the knife-edge, artifact and so on.

LFP utilizes gold nanoparticle of 40-nm size and achieve to measure the focal spot with the only several hundred nanometers with high NA lens (~1.4) with high precision.


  • Only one
  • High resolution (40nm; the size of a nanoparticle)
  • Applicable to High NA focusing lens ( ~ 1.4)
  • Compact sensor with 26 mm height which can operate on a microscope stage
  • No adjustment is required.
  • Principle with accurate measurement(Perfect aberration-free, minimized artifact)
  • 3D measurement


  • Laser Microscope
  • Laser machining
  • Laser fabrication
  • Optical memory
  • Optical tweezers
  • Optical setup overall
  • Variety of microscope objective lenses including liquid immersion lenses


Part List

  • LFP sensor including consumable probe head
  • Scanner (If you selected)
  • Controller
  • Laptop PC
  • Cables

LFP sensor

LFP sensor
Sensor Model LFP-UV-111100 LFP-VIS-166145 LFP-NIR-166145
Laser wavelength 200 nm ~ 400 nm 400 nm ~ 1100 nm 1000 nm ~ 1700 nm
Probe Gold nanoparticl 40 nm Gold nanoparticl 40 nm Gold nanoparticl 4 0nm
Number of Probe
(in the area of beam illudiation, Φ100μm)
> 5 > 5 > 5
NALFP 1.11 1.66 1.66
NAcutoff 1.00 1.45 1.45
Photosensitivity (V/nW) (typ.) TBD TBD TBD
Cutoff frequency of Amp (Hz) 160 160 160
Gain of Amplifier 100M 100M 100M
Size (mm) Φ30 H31 Φ30 H26 Φ30 H26
Weight (g) 55 50 50


Scanner Model TBD XYZ TBD XY
Axis x/y/z x/y
Drive type Piezoelectric element Piezoelectric element
Stroke (μm) 120/120/60 120/120
Resonat frequency (Hz)
at 50g load
155/155/155 155/155
Repetablility (nm) ±5/±5/±5 ±5/±5
Poisition sensor Capacitive sensor Capacitive sensor
Aperture (mm) Φ30 Φ30
Size (mm) □100 H26 □100 H26
Weight (kg) 0.5 0.6


Output port for scanner drive Drive x 3ch(SMB)
Position sensor x 3ch(TJM)
Drive x 2ch(SMB)
Position sensor x 2ch(TJM)
AO(16bit,-10V to 10V) x 1ch, (TJM)
Pulse output x 1ch (TJM)
AO(16bit,0V to 10V) x 3ch(TJM)
Pulse output x 3ch (NBC)
Feedback control type PI Analog PI Analog N.A.
Input sensor port 1ch (BNC) 1ch (BNC) 1ch (BNC)
Input dynamic range 16bit 16bit 16bit
PC communication bus USB USB USB
Power supply AC100 ~ 120V /
AC200 ~ 240V selection
AC100 ~ 120V /
AC200 ~ 240V selection
AC100 ~ 120V /
AC200 ~ 240V selection
Power comsumption 100 VA 100 VA 50 VA
Size (mm) W236×D388×H140 W236×D388×H140 TBD
Weight (kg) 5.4 5.4 TBD

Procedure of operation

Coming soon.

Original paper

Taisuke Ota
“Laser focal profiler based on forward scattering of a nanoparticle”
Opt. Commun. 411, 59-64 (2018)