Power absorption monitor (DGTD) - Simulation object

Absorption monitor can be used to measure the spatial distribution of the absorbed power and its volume integral, the total absorbed power. It also provides the total energy stored within the volume of the monitor.

General tab

• USE LINEAR WAVELENGTH SPACING: By default, data is recorded at linearly spaced points with respect to frequency. Selecting this option spaces data at linearly spaced points with respect to wavelength.
• USE SOURCE LIMITS: When checked these monitors use the source limits. When unchecked, the frequencies/wavelengths at which to record data can be set using the pull-down menus and boxes below them.
• FREQUENCY POINTS: Set to choose the number of frequency points at which to record data.

Geometry tab

Volume Type

• SOLID : Select the target solid. The reference geometry is the volume of the selected solid.
• DOMAIN : Select the target domain. This is a volume enclosed by the target domain(s). If the target domain is DOMAIN 3, type 3. If the target domain is DOMAIN 3 and DOMAIN 5, enter 3,5.
• ALL DOMAINS : The target volume is the whole simulation region

Results returned

• DENSITY: Dataset containing Pabs, the spatial distribution of the fraction of absorbed power per cubic meter, normalized to the source power (unit: \( m^{-3}\)).
  $$ P_{abs} (\vec r, \omega)= \frac{-0.5 \omega \vert E(\vec r, \omega) \vert ^2 imag( \varepsilon (\vec r, \omega) )}{sourcepower(\omega)} $$

• TOTAL: Dataset containing Pabs_total and W_total
  
  • Pabs_total: the fraction of the total absorbed power within the monitor volume, normalized to the source power (unit: unitless)
    $$ P_{abs}^{total} (\omega) = \int_V P_{abs} (\vec r, \omega) d \vec r = \frac{-0.5 \omega }{ sourcepower(\omega) } \int_V imag( \varepsilon ( \vec r, \omega ) ) \vert E(\vec r, \omega) \vert ^2 d \vec r$$
  • W_total:
    $$ W_{total} (\omega) = \int_V real( \varepsilon ( \vec r, \omega )) \vert E ( \vec r, \omega ) \vert ^2 d \vec r$$
    W_total is related to the spectral energy density in the electric field, defined by
    $$ \frac{1}{2} \int_V real( \varepsilon ( \vec r, \omega )) \vert E ( \vec r, \omega ) \vert ^2 d \vec r = \frac{1}{2} W_{total} (\omega) $$
    
    where \( \varepsilon\) and \( E \) are the permittivity and electric field in the monitor volume \( V \), and \( sourcepower(\omega)\) is the power injected by the source.