cheng_2018
==========

S\. Cheng, G\. Chatterjee, F\. Tellkamp, A\. Ruehl and R\. J\. D\. Miller, "Multi\-octave supercontinuum generation in YAG pumped by mid\-infrared, multi\-picosecond pulses", Opt\. Lett\. 43, 4329 \(2018\)

`Source record <https://github.com/LupoLab/optmat/blob/main/src/optmat/data/sources/cheng_2018.toml>`__ · :doc:`Catalogue </the-data/sources>` · :doc:`Review register </register>`

DOI: `10\.1364/ol\.43\.004329 <https://doi.org/10.1364/ol.43.004329>`__

**Source kind:** measurement

**Recorded technique:** Supercontinuum generation in 5\-15\-cm YAG crystals by near\-transform\-limited 3\.0\-ps pulses at 2\.05 um \(Ho\:YLF regenerative amplifier, 1 kHz\) focused with NA 0\.001\-0\.005 \(50\-100 cm lenses and an iris\); spectra 200 nm \- 4\.3 um, SHG\-FROG of the output\. A simple rate\-equation estimate \(Keldysh ionization seeding a Drude avalanche\) sets the breakdown intensity and so the NA\.

**Materials in structured entries:** YAG

**Dataset quantities:** avalanche\_coefficient, band\_gap, damage\_threshold\_energy, damage\_threshold\_intensity, electron\_collision\_time, multiphoton\_ionization\_cross\_section

**Contents:** 6 datasets; 1 formula.

Curation notes
--------------

Journal pages 4329\-4332 = PDF pages 1\-4\. Identity validated\.

MEASURED\: 'The filament formation was initiated at the rear end of the 15 cm YAG crystal for a pump energy of ~17 uJ and was found to shift towards the front end of the crystal upon increasing the pump energy until ~175 uJ, which was determined as the threshold for irreversible crystal damage\. At this energy, the filament started ~5 cm from the front end of the crystal' \(p\. 4330\)\: recorded as a bulk damage\-threshold energy \(15\-cm crystal, NA ~0\.005, 3\.0 ps, 2\.05 um, 1 kHz; the damage criterion and the number of shots are not stated\)\. The continuum at 150 uJ spans 500 nm \- 3\.5 um at \-30 dB \(to 4\.5 um\), 1\.9 % rms over 20 min, \>60 % efficiency with ~1 uJ above 2\.4 um at 120 uJ \(no curated quantity\)\. Crystal orientation and polarization not stated\.

RATE\-EQUATION ESTIMATE \(p\. 4330, inputs assumed\)\: 'YAG with a bandgap energy of U\_i = 6\.5 eV \[4,18\]' \(silva\_2012; Xu and Ching, Phys\. Rev\. B 59, 10530 \(1999\)\); the multiphoton asymptote 'W\_MPI = sigma\_11 I^11, where sigma\_11 = 1\.3 x 10^\-126 s^\-1 \(W/cm2\)^\-11 for rho\_0 = 7 x 10^22 cm^\-3 \[4\]'\: silva\_2012 prints neither \(its rates are in the supplementary information, not in the library\); 'an estimated collision time tau\_c = 3 fs \[4\] yields an inverse Bremsstrahlung coefficient of sigma\_IB = 2\.06 x 10^\-17 cm2'; the result, a threshold I\_th ~ 3 x 10^11 W/cm2 for the 3\-ps pulse, where the density reaches 'the plasma critical density rho\_c = 2\.6 x 10^20 cm^\-3', so the NA must be \<~ 0\.005 for ~10 P\_cr at \<~ 1e11 W/cm2\. The background neutral density rho\_0 = 7e22 cm^\-3 is not recorded as an atom\_density dataset\: 'neutral density' does not say whether atoms or formula units are counted \(a vocabulary gap, reported\)\.

CHECKS \(2026\-09\-26\)\: sigma\_IB = e^2 tau\_c/\(m\_e n0 eps0 c \(1 \+ omega0^2 tau\_c^2\)\) = 3\.70e\-17/n0 cm2 at 2\.05 um, 2\.06e\-17 for n0 = 1\.80 \(n0 not stated\); rho\_c = omega0^2 eps0 m\_e/e^2 = 2\.65e20 cm^\-3 \(printed 2\.6e20\); 6\.5 eV/0\.605 eV = 10\.7, so 11 photons\. silva\_2012 gives sigma = 2\.6e\-20 cm2 at 3\.1 um for the same tau\_c, which is not the Drude value \(see silva\_2012\)\.

**Recorded bibliographic identity status:** VALIDATED. This concerns identification of the source; it does not establish the scientific correctness of its contents.

Datasets
--------

cheng\_2018/damage\_energy
~~~~~~~~~~~~~~~~~~~~~~~~~~

.. code-block:: text

   {
     "id": "damage_energy",
     "material": "YAG",
     "table": "text",
     "quantity": "damage_threshold_energy",
     "unit": "uJ",
     "abscissa": "duration",
     "abscissa_unit": "ps",
     "use": "primary",
     "parameters": {
       "site": "bulk",
       "criterion": "irreversible crystal damage (not further specified)",
       "wavelength_nm": 2050,
       "numerical_aperture": 0.005,
       "shots": "not stated (1 kHz)"
     }
   }

1 inline points in the source record.

p\. 4330\: '~175 uJ, which was determined as the threshold for irreversible crystal damage' in the 15\-cm crystal with NA ~0\.005 \(Rayleigh length ~12 cm\); pulse 3\.0 ps FWHM \(FROG, Fig\. 5\)\. Approximate \('~'\); uncertainty not stated\.

cheng\_2018/model\_band\_gap
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. code-block:: text

   {
     "id": "model_band_gap",
     "material": "YAG",
     "table": "text",
     "quantity": "band_gap",
     "unit": "eV",
     "abscissa": "none",
     "use": "check",
     "reproduced_from": [
       "silva_2012",
       "Y.-N. Xu and W. Y. Ching, Phys. Rev. B 59, 10530 (1999)"
     ],
     "parameters": {
       "kind": "assumed",
       "assumed": true
     }
   }

1 inline points in the source record.

p\. 4330\: 'for YAG with a bandgap energy of U\_i = 6\.5 eV \[4,18\]'\.

cheng\_2018/model\_sigma11
~~~~~~~~~~~~~~~~~~~~~~~~~~

.. code-block:: text

   {
     "id": "model_sigma11",
     "material": "YAG",
     "table": "text",
     "quantity": "multiphoton_ionization_cross_section",
     "unit": "s-1 (W/cm2)-11",
     "abscissa_unit": "nm",
     "use": "check",
     "reproduced_from": [
       "silva_2012"
     ],
     "parameters": {
       "photons": 11,
       "assumed": true
     }
   }

1 inline points in the source record.

p\. 4330\: 'W\_MPI = sigma\_11 I^11, where sigma\_11 = 1\.3 x 10^\-126 s^\-1 \(W/cm2\)^\-11 for rho\_0 = 7 x 10^22 cm^\-3 \[4\]', the low\-intensity asymptote of their Keldysh rate at 2\.05 um \(Fig\. 1a\)\. The printed unit makes it a rate per atom; 'for rho\_0' says the per\-volume rate uses rho\_0 = 7e22 cm^\-3\. silva\_2012's main text does not print it \(its Supplementary Fig\. S2 may\)\.

cheng\_2018/model\_collision\_time
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. code-block:: text

   {
     "id": "model_collision_time",
     "material": "YAG",
     "table": "text",
     "quantity": "electron_collision_time",
     "unit": "fs",
     "abscissa": "none",
     "use": "check",
     "reproduced_from": [
       "silva_2012"
     ],
     "parameters": {
       "assumed": true
     }
   }

1 inline points in the source record.

p\. 4330\: 'an estimated collision time tau\_c = 3 fs \[4\]'\.

cheng\_2018/model\_avalanche\_cross\_section
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. code-block:: text

   {
     "id": "model_avalanche_cross_section",
     "material": "YAG",
     "table": "text",
     "quantity": "avalanche_coefficient",
     "unit": "cm2",
     "abscissa_unit": "nm",
     "use": "check",
     "parameters": {
       "definition": "sigma_IB in W_AI = sigma_IB I/U_i, d rho/dt = W_OFI(I)(rho_0 - rho) + W_AI(I) rho",
       "assumed": true
     }
   }

1 inline points in the source record.

p\. 4330\: 'W\_AI = sigma\_IB I/U\_i \.\.\. according to the Drude model, where an estimated collision time tau\_c = 3 fs \[4\] yields an inverse Bremsstrahlung coefficient of sigma\_IB = 2\.06 x 10^\-17 cm2'; the Drude value for n0 = 1\.80 \(source notes\)\.

cheng\_2018/model\_breakdown\_intensity
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

.. code-block:: text

   {
     "id": "model_breakdown_intensity",
     "material": "YAG",
     "table": "text",
     "quantity": "damage_threshold_intensity",
     "unit": "W/cm2",
     "abscissa": "duration",
     "abscissa_unit": "ps",
     "use": "check",
     "parameters": {
       "site": "bulk",
       "criterion": "calculated: electron density reaching rho_c = 2.6e20 cm^-3",
       "wavelength_nm": 2050
     }
   }

1 inline points in the source record.

p\. 4330 \(Fig\. 1b\)\: calculated, 'beyond a threshold intensity of I\_th ~ 3 x 10^11 W/cm2 the electron density rho\(t\) rapidly reaches the plasma critical density rho\_c = 2\.6 x 10^20 cm^\-3 for the duration of our pump pulse'\. A model estimate\.

Formulas
--------

cheng\_2018/rate\_equation
~~~~~~~~~~~~~~~~~~~~~~~~~~

.. code-block:: text

   {
     "id": "rate_equation",
     "material": "YAG",
     "equation": "p. 4330 (text)",
     "printed": "d rho/dt = W_OFI(I)(rho_0 - rho) + W_AI(I) rho; W_MPI = sigma_11 I^11; W_AI = sigma_IB I/U_i",
     "variable": "rho: electron density; rho_0 the background neutral density; W_OFI the Keldysh optical-field-ionization rate (refs. 1, 17)",
     "coefficients": {
       "U_i": "6.5 eV",
       "sigma_11": "1.3e-126 s^-1 (W/cm^2)^-11",
       "rho_0": "7e22 cm^-3",
       "tau_c": "3 fs",
       "sigma_IB": "2.06e-17 cm^2",
       "rho_c": "2.6e20 cm^-3"
     },
     "reproduced_from": [
       "silva_2012",
       "couairon_2005"
     ],
     "check": "sigma_IB and rho_c checked (source notes); I_th ~ 3e11 W/cm2 not recomputed (the Keldysh rate is a figure)."
   }

The library text renders the avalanche term as W\_AI\(I\) rho~ \(a lost glyph\)\.

Corrections
-----------

No dataset errata are recorded in this source record.

Formula corrections, where recorded, appear with their formulas above. Curation notes may also discuss corrections or unresolved interpretation. Consult the :doc:`review register </register>` for the checks and decisions.